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.rs .\" Troff code generated by TPS Convert from ITU Original Files .\" Not Copyright (~c) 1991 .\" .\" Assumes tbl, eqn, MS macros, and lots of luck. .TA 1c 2c 3c 4c 5c 6c 7c 8c .ds CH .ds CF .EQ delim @@ .EN .nr LL 40.5P .nr ll 40.5P .nr HM 3P .nr FM 6P .nr PO 4P .nr PD 9p .po 4P .rs \v'|.5i' .LP \fBMONTAGE : FIN DU \(sc 5.6.10 EN T\*\|ETE DE CETTE PAGE\fR .sp 2P .LP \v'22P' \fB6\fR \fBPacket layer\fR .RT .sp 2P .sp 1P .RT .LP .EF '% Fascicle\ VIII.2\ \(em\ Rec.\ X.32'' .OF '''Fascicle\ VIII.2\ \(em\ Rec.\ X.32 %' .sp 1P .LP 6.1 \fIScope and field of application\fR .sp 9p .RT .PP The formats and the procedures at the packet layer shall be in accordance with \(sc\(sc\ 3, 4, 5, 6 and\ 7 of Recommendation\ X.25 with additions as noted in this section and in \(sc\ 7 of this Recommendation. .PP If identification and authentication are done at the packet layer, identification and authentication of the identity of both the DTE and DCE will cease to apply when a failure on the physical layer and/or link layer is detected. .PP Some DTEs may choose to use the registration procedure for \fIon\(hyline\fR \fIfacility registration\fR \| immediately after the switched access path has been established and the link has been set up. .RT .sp 1P .LP 6.2 \fIUse of registration packets for identification of DTE and/or DCE\fR \fIand for conveyance of X.32 optional user facilities\fR .sp 9p .RT .PP The registration procedure can be used for DTE and DCE identification at the packet layer. The \fIregistration request\fR \| packet is used to convey identification protocol elements from the DTE to the DCE. The .PP \fIregistration confirmation\fR \| packet is used to convey identification protocol elements from the DCE to the DTE. .PP When using \fIregistration\fR \| packets for DCE identification, it is necessary for the DTE to send a \fIregistration request\fR \| packet in order to give the DCE an opportunity to identify itself. .PP Whenever DCE identification is being done via the registration procedure, a \fIregistration confirmation\fR \| packet must be sent after the identification protocol has been completed in order for the registration procedure to be completed. If the DCE identification was not successful, this packet may contain identification protocol elements to begin the DCE identification procedure again, if allowed. .PP The identification protocol may be used for DTE identification and DCE identification at the same time. When this occurs, a registration packet may carry elements for both directions of identification simultaneously. .PP A DTE may specify X.32 optional user facilities in registration packets. .PP Descriptions of the identification protocol elements and X.32 facilities are listed in \(sc\ 7.2. .bp .PP When the \fIregistration request\fR \| or the \fIregistration confirmation\fR \| packet is used for identification and/or the conveyance of X.32 optional user facilities, the elements and/or facilities (see \(sc\ 7.3) are carried in the registration field. .PP Registration packets may be used to perform identification, conveyance of X.32 facilities, and on\(hyline facilities negotiation in the same packets, subject to the restriction of \(sc\ 7.1.2, below (see \(sc\ 7.3 of Recommendation\ X.25). .RT .sp 1P .LP 6.3 \fIIdentification and authentication of the DTE using the NUI\fR \fIselection facility in call set\(hyup packets\fR .sp 9p .RT .PP The \fINUI selection\fR \| facility in \fIcall set\(hyup\fR \| packets can be used for DTE identification on a per virtual call basis. It can also be used in addition to one of the prior\(hyto\(hyvirtual\(hycall DTE identification methods. This NUI identification remains in effect for the lifetime of the virtual call and is independent of any previous NUI identification on the interface. Subsequent call requests on the switched access path will either revert to the prior DTE service on the interface or receive a DTE service associated with a NUI. .PP The \fINUI selection\fR \| facility parameter may contain as the \fIDTE\fR \fIidentity\fR \| either a user identifier plus a password assigned by the network to the DTE, or only a password assigned by the network to the DTE. The formats of the user identifier and the password are national matters. The following cases describe the operation of the \fINUI selection\fR \| facility: .RT .LP 1) When a \fIDTE identity\fR \| has been established using a prior\(hyto\(hyvirtual\(hycall DTE identification method, the \fINUI selection\fR facility may be used if the \fINUI subscription\fR \| and/or the \fINUI override\fR \| facilities are set by the network. In this case, the \fINUI selection\fR \| facility applies conforming to the procedures described in Recommendation\ X.25 (see \(sc\ 6.21/X.25). .LP 2) When a \fIDTE identity\fR \| has not been established using a prior\(hyto\(hyvirtual\(hycall identification method and the \fINUI\fR \fIselection\fR \| facility is used, the \fIidentified DTE\fR \| service (see \(sc\ 3.4) is selected (when supported by the network). Two subcases are possible: .LP a) \fINUI override\fR \| facility is set by the network when a \fIcall request\fR \| packet containing a valid NUI is sent, the features subscribed to by the DTE identified by that NUI and associated with that NUI apply to the virtual call; .LP b) \fINUI override\fR \| facility is not set by the network when a \fIcall request\fR \| packet containing a valid NUI is sent, the default \fIX.25 subscription set\fR \| applies to the virtual call. .PP In both cases a) and b), the NUI remains in effect only for the lifetime of the virtual call. .LP \fB7\fR \fBX.32 procedures, formats and facilities\fR .sp 1P .RT .sp 2P .LP 7.1 \fIIdentification protocol\fR .sp 1P .RT .sp 1P .LP 7.1.1 \fIProtocol elements\fR .sp 9p .RT .PP The identification protocol is for exchanging identification and authentication information in one or more pairs of messages. The two parties involved in this protocol are called the questioning party and the challenged party. .PP Two security options are defined: the basic option described as \fIsecurity grade\ 1\fR \| and an enhanced option described as \fIsecurity grade\ 2\fR . The identification and authentication information are encoded in the following protocol elements: .RT .LP a) The identity element (ID) is a string of octets representing the DTE or DCE identity (see \(sc\(sc\ 2.2.1 and\ 2.2.2, respectively) of the challenged party. .LP b) The signature element (SIG) of the identity is a string of octets associated with the identity and used for authentication of the identity. It is assigned for a period of time by the authority that assigns the identity and may be changed from time to time. For example, the SIG may be a password or the result of an encryption process applied to the identity element (ID) of the challenged party. .LP c) The random number element (RAND) is a string of octets which is unpredictable for each identification exchange. It is used only in the security grade\ 2 option. .bp .LP d) The signed response element (SRES) of the challenged party is the reply to the RAND protocol element by the questioning party. It is used only in the security grade\ 2 option. .LP e) The diagnostic element (DIAG) is the result of the identification process and is transmitted by the questioning party at the end of the process. .PP The format of these elements is shown in \(sc\ 7.3. .PP The sizes of values of the identity, signature and random number elements are a national matter and depend on a number of factors including: .RT .LP a) whether the authentication is of DTE identity or DCE identity, .LP b) the grade of security, .LP c) the method of identification, .LP d) the possibilities of future improvements in computational techniques, and .LP e) whether the PSPDN directly assigns DTE identities or adopts, through pre\(hyarrangement, the DTE identities assigned by the PSN or another authority. .sp 1P .LP 7.1.2 \fIIdentification protocol procedure\fR .sp 9p .RT .PP The first message of a pair is transmitted by the challenged party. The second message of the pair is transmitted by the questioning party. Security grade\ 1 provides a single exchange of elements ID [,\ SIG], and DIAG, whereas security grade\ 2 uses an additional exchange of RAND and SRES elements to provide a greater degree of security. .PP \fINote\fR \ \(em\ In both security grades\ 1 and 2, SIG may be omitted if not required by the questioning party. If it is not required, its presence is not considered in error. .PP The identification protocol elements are passed between the parties in either a sequence of XID command frames or registration packets. Networks may offer either or both methods of security exchange, but an entire identification exchange must be done entirely with only one method. .PP The identification protocol may be used for DTE identification simultaneously but independently of its use for DCE identification. When this occurs, a registration packet or XID frame may carry elements for both directions of identification simultaneously. .PP The identification established using the identification protocol applies for the duration of the switched access. That is, once the DIAG element indicating acceptance of the DTE/DCE identity has been sent, the switched access path must be disconnected before another attempt to use the identification protocol to identify that challenged party can be made. .PP If the identification protocol is not successful, that is, the DIAG element indicates refusal of the DTE/DCE identity, the questioning party should disconnect the switched access path. In the case of security grade\ 1, a network may allow up to three retries of the identification protocol (i.e.,\ the DIAG element indicates refusal of the DTE/DCE identity) before the switched access path is disconnected when the network is the questioning party. For security grade\ 2, only one attempt to perform the identification protocol is permitted when the network is the questioning party. .PP The actions of the DCE when acting as the challenged or questioning party are further described by the state diagrams and tables in Annex\ A. .PP The security grade applied on a particular switched connection is determined by the subscription of the DTE with the Administration. It is not negotiable on a per call basis. Not all networks will offer both security grade options. The use of certain optional features may be restricted to a particular security grade. A positive and secure DTE identification is limited to the security of the switched access path, particularly in dial\(hyout\(hyby\(hythe\(hyPSPDN operation. .PP In order to avoid situations in which both parties are waiting for the other to identify first, these principles will be followed: .RT .LP a) Each party should send its identity, if capable and willing, at the earliest opportunity. However, the called party is not required to send its own identity before complete identification of the calling party. .LP b) If the calling party does not send its identity, the called party has a choice of operating a service not requiring identification or disconnecting the switched connection. .PP Security grade 1 involves a single pair of messages as shown in Figure\ 12/X.32. First, the challenged party sends its identity (ID) and, if required, its signature (SIG). The questioning party responds with the diagnostic (DIAG). .bp .LP .rs .sp 11P .ad r \fBFigure 12/X./32, p.\fR .sp 1P .RT .ad b .RT .PP As shown in Figure 13/X.32, security grade 2 involves an additional authentication exchange if the initial response (ID [,\ SIG]) of the challenged party is valid. If ID is an identity unknown to the questioning party or if the SIG element is required by the questioning party but either it is not present or is inconsistent with the claimed identity, then an error diagnostic (DIAG) is issued and the access path is disconnected. Otherwise, the questioning party will generate and send a random number (RAND) which the challenged party will encrypt and return as its signed response (SRES). The .PP questioning party will then decrypt SRES and, if this operation results in a value identical to RAND, the appropriate diagnostic (DIAG) is sent to the challenged party and the identification process is successfully completed. Otherwise, an error diagnostic (DIAG) is returned and the access path is disconnected. .PP \fINote\ 1\fR \ \(em\ It is left for further study whether or not to define, as a mechanism for protecting against specific forms of intrusion, that the value of RAND is odd or even depending on the direction of the switched access call. .PP \fINote\ 2\fR \ \(em\ If the network does not store the public keys of DTEs, the SIG can be used to convey the public key and other information characteristics of the DTE (e.g.,\ indication of security level two is to be used). Private keys of the DTE, if any, are not included in the SIG information. In order to add to the protection, this information can be encrypted via the private key of the network. .PP If on\(hyline facility registration is done simultaneously with identification, the DTE shall do so only in the packet containing SRES. If on\(hyline facility registration is attempted prior to SRES, it will be refused by the network with a cause code value of \fIlocal procedure error\fR . .RT .LP .rs .sp 20P .ad r \fBFigure 13/X.32, p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 1P .LP 7.1.3 \fIIdentification protocol formats\fR .sp 9p .RT .PP The formats for the identification protocol elements are defined in \(sc\ 7.3 of this Recommendation in accordance with \(sc\(sc\ 6 and\ 7 of Recommendation\ X.25. The elements are coded identically in registration packets and XID frames. .RT .sp 2P .LP 7.2 \fIProcedures for X.32 optional user facilities\fR .sp 1P .RT .sp 1P .LP 7.2.1 \fISecure dial\(hyback facility\fR .sp 9p .RT .PP Networks that implement both the dial\(hyin\(hyby\(hythe\(hyDTE and dial\(hyout\(hyby\(hythe\(hyPSPDN operations may provide, as an optional user facility agreed for a period of time, a dial\(hyback procedure. This facility, if subscribed to, combines the dial\(hyin\(hyby\(hythe\(hyDTE operation with the dial\(hyout\(hyby\(hythe\(hyPSPDN operation to offer additional protection when the identity of the DTE becomes known to the network. This procedure allows, in .PP the \fIcustomized\fR \| DTE service, a DTE to use the dial\(hyin\(hyby\(hythe\(hyDTE operation, identity itself, and disconnect. Security is achieved in using the \fIidentity element\fR \| of the identification protocol and a dial\(hyout\(hyby\(hythe\(hyPSPDN to the \fIregistered PSN number\fR . The network uses the dial\(hyout\(hyby\(hythe\(hyPSPDN operation to dial back the DTE using the \fIregistered PSN\fR \fInumber\fR . The DCE identifies itself and the DTE identifies itself again. Some networks may offer the additional feature of limiting the use of the \fIsecure\fR \fIdial\(hyback\fR \|facility to specific hours of operation of the DTE. .PP The grade of security for \fIsecure dial\(hyback\fR \| is not negotiable per switched access call. It is one aspect of the identity and its value is set when pre\(hyregistering to the authority that defines the identity. .PP After the DTE has correctly identified itself to the DCE during dial\(hyin\(hyby\(hythe\(hyDTE, the DCE sends a \fIrequest for dial\(hyback confirmed\fR \| via the \fIdiagnostic element\fR \| of the identification protocol. Then the DTE and network should disconnect the link, if necessary, and then the switched access path as soon as possible. The network should then initiate the dial\(hyback to the DTE as soon as possible by using dial\(hyout\(hyby\(hythe\(hyPSPDN. .PP If, during the dial\(hyin\(hyby\(hythe\(hyDTE operation, the DCE is aware that it cannot perform the dial\(hyback, the DCE will indicate to the DTE that dial\(hyback is not possible. This indication is given via the \fIdiagnostic element\fR \| of the identification protocol. .PP When the DCE disconnects the switched access path on the dial\(hyin\(hyby\(hythe\(hyDTE it starts DCE timer T15. The DCE then attempts the dial\(hyout\(hyby\(hythe\(hyPSPDN operation as soon as possible. The period of timer\ T15, at the end of which the DCE abandons the attempt to dial out to the DTE, is a system parameter agreed for a period of time with the Administration. .PP When the network dials out, the DCE includes a \*Qdial\(hyback indication\*U to the DTE via the \fIdiagnostic element\fR \| of the identification protocol. .PP If the DTE receives an unsolicited dial\(hyback from the DCE, the switched access path may be disconnected. .PP \fINote\fR \ \(em\ As some PSTN networks implement \fIcalling party clear\fR , a PSPDN may wish to restrict dial\(hyback to an outgoing only PSTN port. .RT .sp 1P .LP 7.2.2 \fITemporary location facility\fR .sp 9p .RT .PP \fITemporary location\fR \| is an optional user facility that applies to the DTE/DCE interface for registered DTEs that accept dial\(hyout calls from the PSPDN. .PP This facility can be used to substitute a different switched access number for dial\(hyout\(hyby\(hythe\(hyPSPDN to the DTE other than the \fIregistered PSN\fR \fInumber\fR . The switched access number specified is an X.121 number from the PSN numbering plan. .PP \fINote\fR \ \(em\ Extension of a switched access number to accommodate additional digits, secondary digits, secondary dial tone, or dialling delays as allowed by V.25 and/or X.24 is left for further study. .PP In addition, a DTE may specify, by means of this facility, the periods of time during which it may be reached at a valid number for the PSN. .PP During those periods not identified by this facility, the number used to reach the DTE will be its \fIregistered PSN number\fR . .PP The substitute number goes into effect at the \*Qstay initiation\*U data and time. The substitute number is no longer in effect at the \*Qstay termination\*U date and time. .PP At the expiration of the time given in the \fItemporary location\fR \| facility, the number used for dial\(hyout\(hyby\(hythe\(hyPSPDN reverts to the \fIregistered\fR \fIPSN number\fR . .bp .PP Use of the \fItemporary location\fR \| facility by the called DTE will not cause the \fIcalled line address modified notification\fR \| facility to be inserted in the Call Connected packet. However, the \fIcalled line address modified\fR \fInotification\fR facility will appear in the Call Connected packet according to normal conditions of Recommendation\ X.25. .RT .sp 2P .LP 7.3 \fICoding of the identification protocol elements and X.32\fR \fIfacilities\fR .sp 1P .RT .sp 1P .LP 7.3.1 \fIGeneral\fR .sp 9p .RT .PP The general principles for coding of the identification protocol elements and X.32 facilities are the same as the ones specified for the registration field in \(sc\ 7.1 of Recommendation\ X.25. The statements of \(sc\ 7.1 of Recommendation\ X.25 concerning facilities do not apply to this section. The statements of \(sc\ 7.1 of Recommendation\ X.25 concerning registration elements apply to the identification protocol elements and X.32 facilities in this section. .RT .sp 1P .LP 7.3.2 \fICoding of the identification protocol element and X.32 facility\fR \fIcode fields\fR .sp 9p .RT .PP Table 8/X.32 gives the list of the identification protocol element and X.32 facility codes, the coding for each, and, where applicable, whether this code may be sent by the challenged or the questioning party. .RT .LP .sp 1 .ce \fBH.T. [T7.32]\fR .ce TABLEAU\ 8/X.32 .ce \fBIdentification protocol element and X.32 facility codes\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(84p) | cw(36p) sw(36p) | cw(12p) sw(6p) sw(12p) sw(6p) sw(12p) sw(6p) sw(12p) sw(6p) , ^ | c | c | c | c | c | c | c | c | c | c. T{ Identification element or facility code T} May be sent by Bits challenged party questioning party 8 7 6 5 4 3 2 1 _ .T& lw(84p) | cw(36p) | lw(36p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . Identity element X 1 1 0 0 1 1 0 0 .T& lw(84p) | cw(36p) | lw(36p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . Signature element X 1 1 0 0 1 1 0 1 .T& lw(84p) | cw(36p) | cw(36p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . Random number element X 1 1 0 0 1 1 1 0 .T& lw(84p) | cw(36p) | cw(36p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . Signed response element X 1 1 0 0 1 1 1 1 .T& lw(84p) | cw(36p) | cw(36p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . Diagnostic element X 0 0 0 0 0 1 1 1 .T& lw(84p) | cw(36p) | cw(36p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . Temporary location 1 1 0 1 0 0 0 0 _ .TE .nr PS 9 .RT .ad r \fBTable 8/X.32 [T7.32], p.\fR .sp 1P .RT .ad b .RT .sp 2P .LP .sp 1 7.3.3 \fICoding of the identification protocol element and X.32 facility\fR \fIparameter fields\fR .sp 1P .RT .sp 1P .LP 7.3.3.1 \fIIdentity element\fR .sp 9p .RT .PP The octet following the code field indicates the length, in octets, of the parameter field. The following octets contain the string of octets composing the identity. .RT .sp 1P .LP 7.3.3.2 \fISignature element\fR .sp 9p .RT .PP The octet following the code field indicates the length, in octets, of the parameter field. The following octets contain the string of octets composing the signature. .bp .RT .sp 1P .LP 7.3.3.3 \fIRandom number element\fR .sp 9p .RT .PP The octet following the code field indicates the length, in octets, of the parameter field. The following octets contain the string of octets composing the number which is the random number element. It is binary coded with bit\ 8 of the first octet following the parameter length being the high order bit and bit\ 1 of the last octet being the low order bit. If the number of significant bits of the random number is not octet\(hyaligned, then zeroes precede the most significant bit to make it octet\(hyaligned. .RT .sp 1P .LP 7.3.3.4 \fISigned response element\fR .sp 9p .RT .PP The octet following the code field indicates the length, in octets, of the parameter field. The following octets contain the string of octets composing the number which is the signed response. It is binary coded with bit\ 8 of the first octet following the facility parameter length being the high order bit and bit\ 1 of the last octet being the low order bit. If the number of significant bits of the signed response is not octet\(hyaligned, then zeroes precede the most significant bit to make it octet\(hyaligned. .RT .sp 1P .LP 7.3.3.5 \fIDiagnostic element\fR .sp 9p .RT .PP The coding of the parameter field for the \fIdiagnostic element\fR \| is shown in Table\ 9/X.32. .RT .LP .sp 3 .ce \fBH.T. [T8.32]\fR .ce TABLE\ 9/X.32 .ce \fBCoding of the parameter field for the diagnostic element\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; lw(156p) | cw(72p) . Bits .T& lw(156p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . 8 7 6 5 4 3 2 1 _ .T& lw(156p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . T{ Identification/authentication confirmed T} 0 1 1 1 1 1 1 1 _ .T& lw(156p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . T{ Identification or authentication failed (Note\ 1) \(em\ general T} 1 0 0 0 0 0 0 0 .T& lw(156p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . \(em\ additional 1 X X X X X X X _ .T& lw(156p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . Network congestion (Note 2) 0 0 0 0 0 1 0 1 _ .T& lw(156p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . T{ Identification in use (Note 3) T} 0 0 0 1 0 1 1 1 _ .T& lw(156p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . T{ Dial\(hyback indication (Note 4) T} 0 0 1 1 1 1 1 1 _ .T& lw(156p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . T{ Network congestion for dial\(hyback (Note 4) T} 0 0 0 1 1 0 1 1 _ .T& lw(156p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) | cw(12p) | cw(6p) . T{ Request for dial\(hyback confirmed (Note 4) T} 0 0 0 1 1 1 1 T{ 1 \fINote\ 1\fR \ \(em\ Bits 7 to 1 are for maintenance purposes and are a national matter. Complete specification and provision of this information to a user represents a possible compromise of security by providing details of authentication failure. .parag \fINote\ 2\fR \ \(em\ Replacement of this \fIcall progress\fR signal is for further study in close liaison with the revision of Recommendation\ X.96. .parag \fINote\ 3\fR \ \(em\ Whether multiple switched connections can be simultaneously active using the same \fIDTE identity\fR is for further study. .parag \fINote\ 4\fR \ \(em\ Used only in conjunction with the \fIsecure dial\(hyback\fR facility (see \(sc\ 7.2.1). .parag T} _ .TE .nr PS 9 .RT .ad r \fBTable 9/X.32 [T8.32], p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 1P .LP 7.3.3.6 \fITemporary location facility\fR .sp 9p .RT .PP The octet following the code field indicates the length, in octets, of the parameter field. .PP The parameter field consists of one or more instances of temporary location requested by the DTE. .PP For each instance of temporary location, the first 5 octets indicate the date and time of the stay initiation. The next 5\ octets indicate the date and time of the stay termination. The octet following the stay termination indicates the number of semi\(hyoctets in the switched access number and is binary encoded. The following octets contain the switched access number. .PP Date and time of initiation/termination is a string of 10 decimal digits expressing the coordinated universal time (UTC) and has the form .PP YYMMDDhhmm. YY is the two low\(hyorder digits of the Christian era year, and MM, DD, hh, and\ mm are the month, day, hour, and minute, respectively. The 10\ decimal digits are BCD encoded in 5\ octets with the first digit of the year encoded into bits\ 8 to\ 5 of the first octet and the last digit of the minute encoded into bits\ 4 to\ 1 of the fifth\ octet. .PP A value of all zeros for stay initiation will indicate the DTE's desire for immediate initiation. .PP A value of all zeros for stay termination will indicate the DTE's desire for the switched number to remain in effect until subsequent replacement (i.e.,\ permanently). .PP \fINote\fR \ \(em\ Some networks may only permit the stay termination and/or stay initiation fields to contain all zeros. In that case, the number of instances of temporary location is limited to one. .PP The switched access number is coded as a series of semi\(hyoctets. Each semi\(hyoctet contains either a digit in binary coded decimal or a special value in the range 1010\(hy1111 binary. .PP \fINote\fR \ \(em\ The special values may be used to accommodate the capabilities of V.25 and/or X.24, particularly in specifying secondary dial .PP tone and dialling delays. Such use is left for further study. .PP If the switched access number contains an odd number of semi\(hyoctets, it is followed by a semi\(hyoctet containing zeros. .PP A switched number length of zero will indicate that the DTE is unavailable. .RT .sp 1P .LP 7.4 \fISecurity grade 2 method\fR .sp 9p .RT .PP The authentication method in security grade 2 provides for the use of encryption to prevent unauthorized access subject to the constraints of unit cost and computation time. One example of a public key encryption technique which could be used for this purpose is given in Appendix\ II. The selection and use of security grade\ 2 algorithms is a national matter. .PP \fINote\fR \ \(em\ Further study, in close cooperation with ISO/TC 97/SC 20, will define the characteristics and length constraints of the various numbers and parameters to be used in security grade\ 2 algorithms. The definition of the parameters of an algorithm should strike a balance between the cost and the complexity of the algorithm, and the value of that which is protected. The goal is to make the cost of breaking the code exceed the cost of obtaining the network resources by authorized means. .RT .sp 1P .LP 7.5 \fIDCE timer T14\fR .sp 9p .RT .PP The DCE may support a timer T14, the value of which should be made known to the DTE. .PP At the expiration of timer T14, the DCE will disconnect the link, if connected, then the switched access path. .PP Timer T14 is started whenever a switched access path is established. Timer T14 is stopped when either the \fIDTE identity\fR \| is established or a virtual call(s) is established which is not to be charged to the local DTE. In the latter case, timer\ T14 will be restarted when no assigned logical channels are active. .PP The relationships of timer T14 to the different methods of DTE identification are illustrated in Appendix\ III. .PP The period of timer T14 shall be network dependent. .RT .sp 1P .LP 7.6 \fIDCE timer T15\fR .sp 9p .RT .PP Timer T15 is used in conjunction with the secure \fIdial\(hyback\fR \| facility (see \(sc\ 7.2.1). .PP The period of timer T15 is left for further study. .bp .RT .ce 1000 ANNEX\ A .ce 0 .ce 1000 (to Recommendation X.32) .sp 9p .RT .ce 0 .ce 1000 \fBActions taken by the DCE in the roles of questioning\fR .sp 1P .RT .ce 0 .ce 1000 \fBand challenged parties for security grade 1\fR .ce 0 .ce 1000 \fBand security grade 2 identifications\fR .ce 0 .LP A.1 \fIIntroduction\fR .sp 1P .RT .PP This annex specifies the actions taken by the DCE when it acts as the questioning and challenged parties for security grade\ 1 and security grade\ 2 identifications. When performing the identification procedure described in \(sc\ 7.1.2, the DCE shall act as described in this annex. .PP \fINote\fR \ \(em\ As the identification protocol is symmetrical and should be used by the DTE in the same manner as the DCE, the actions of the DTE should correspond directly to the actions defined for the DCE. .PP The identification protocol is presented as a succession of state diagrams and corresponding tables. .PP In this annex, a DIAG element is considered as positive when its parameter field means \fIidentification/authentication confirmed\fR , \fIrequest for\fR \fIdial\(hyback confirmed\fR , or \fIdial\(hyback indicator\fR \| (see \(sc\ 7.3.3.5). It is considered as negative in other cases. .RT .sp 1P .LP A.1.1 \fISymbol definition of state diagrams\fR .sp 9p .RT .LP .rs .sp 15P .ad r \fBFigure T0706570\(hy88, p.\fR .sp 1P .RT .ad b .RT .sp 1P .LP A.1.2 \fIDefinition of actions\fR .sp 9p .RT .PP In each table, the actions taken by the DCE as the questioning party or the challenged party are indicated in the following way: .RT .LP NORMAL: Normal event; protocol elements received are handled as described in \(sc\ 7.1.2. .LP DISCARD: Received message is discarded. .LP RAND: RAND transmitted. .LP Positive DIAG: Positive DIAG transmitted. .LP Negative DIAG: Negative DIAG transmitted. .LP ID [, SIG]: ID [, SIG] transmittted. .LP SRES: SRES transmitted. .PP Each entry in the tables in this annex gives, first, the action taken, if any, then an arrow indicating the transition, and finally, the state that the DCE as the questioning or challenged party will enter. .bp .sp 2P .LP A.2 \fISecurity grade 1 identification\fR .sp 1P .RT .sp 1P .LP A.2.1 \fIDCE acting as the questioning party\fR .sp 9p .RT .PP The DCE acts as the questioning party for security grade 1 when it offers \fIidentified\fR \|or \fIcustomized\fR \| DTE service via the XID or registration DTE identification method with grade\ 1 authentication. Four states are defined for describing the procedures the DCE uses: .RT .LP a) \fIq11 \(em Waiting for ID [, SIG] (grade 1)\fR .LP This is the initial state of the DTE identification process. It is entered after the switched connection is established and, when the registration procedure DTE identification method is used, after the link layer is set up. In this state, the DCE expects to receive the ID (and possibly SIG) element(s) from the DTE. If the DCE allows retrying the identification protocol, this state is also entered when a DTE identification attempt has failed and the limit of retries has not been exhausted. .LP b) \fIq12 \(em Evaluating ID [, SIG] (grade 1)\fR .LP In this state, the DCE determines whether or not the DTE identity that was presented in the ID (and possibly SIG) element(s) is acceptable. The result is the transmission by the DCE to the DTE of the DIAG element, which has as its value the success or not of the acceptability evaluation. .LP c) \fIq13 \(em DTE identification successful (grade 1)\fR .LP In this state, the DCE provides the \fIidentified\fR \| or \fIcustomized\fR \| DTE service to the identified DTE. The DCE remains in this state until the switched connection is disconnected. .LP d) \fIq14 \(em DTE identification unsuccessful (grade 1)\fR .LP In this state, the DCE does not provide the \fIidentified\fR \| or \fIcustomized\fR \| DTE service (unless NUI is used on a per virtual call basis for the \fIIdentified\fR \| DTE service) but may provide the \fINonidentified\fR \| DTE service if it is supported. The DCE enters this state when the last DTE identification attempt allowed by the retry limit has failed. The DCE remains in this state until the switched connection is disconnected. .PP Figure A\(hy1/X.32 provides the state diagram for the DCE acting as the questioning party in the case of security grade\ 1 identification. .PP The actions to be taken by the DCE acting as the questioning party for security grade\ 1 identification, when one of the listed events occurs, are indicated in Table\ A\(hy1/X.32. .RT .LP .rs .sp 24P .ad r \fBFigure A\(hy1/X.32, p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [T9.32]\fR .ce TABLE\ A\(hy1/X.32 .ce \fBActions taken by the DCE as the questioning party (security .ce \fBgrade\ 1)\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; lw(60p) | cw(42p) | cw(42p) | cw(42p) | cw(42p) . T{ State of the DCE acting as the questioning party \| \ \| \ Protocol element received by the DCE or decision by the DCE T} T{ \ \| \ \| q11 Waiting for ID\ [,\ SIG] (grade\ 1) T} T{ \ \| \ \| q12 Evaluating ID\ [,\ SIG] (grade\ 1) T} T{ \ \| \ \| q13 Identification successful (grade\ 1) T} T{ \ \| \ \| q14 DTE identification unsuccessful (grade\ 1) (see Note\ 1) T} _ .T& lw(60p) | cw(42p) | cw(42p) | cw(42p) | cw(42p) . ID [,\ SIG] NORMAL\|\(raq12 DISCARD\|\(raq12 DISCARD\|\(raq13 DISCARD\|\(raq14 _ .T& lw(60p) | lw(42p) | lw(42p) | lw(42p) | lw(42p) . T{ DCE checking of the ID\ [,\ SIG] is complete T} T{ //////////////// //////////////// //////////////// //////////////// //////////////// //////////////// T} T{ Positive DIAG \(raq13 or negative DIAG \(raq14 or \(raq11 (see Note\ 2) T} T{ //////////////// //////////////// //////////////// //////////////// //////////////// //////////////// T} T{ //////////////// //////////////// //////////////// //////////////// //////////////// //////////////// \fINote\ 1\fR \ \(em\ When in this state, the DCE should disconnect the switched access path when it is sure that the DIAG element has been received by the challenged party or the challenged party is out\(hyof\(hyorder. .parag \fINote\ 2\fR \ \(em\ Depending on whether or not ID and/or SIG are recognized as correct by the DCE. When negative DIAG, go to q11 until the retry limit has been reached. .parag T} _ .TE .nr PS 9 .RT .ad r \fBTable A\(hy1/X.32 [T9.32], p.\fR .sp 1P .RT .ad b .RT .sp 1P .LP .sp 3 A.2.2 \fIDCE acting as the challenged party\fR .sp 9p .RT .PP The DCE acts as the challenged party for security grade 1 when it identifies itself to the DTE via the XID or registration DCE identification method with grade\ 1 authentication. Four states are defined for describing the procedures the DCE uses: .RT .LP a) \fIc11 \(em Initial challenged (grade 1)\fR .LP This is the initial state of the DCE identification process. It is entered after the switched connection is established, and, .LP when the registration procedure DCE identification method is used, after the link layer is set up. In this state, the DCE transmits the ID (and possibly SIG) element(s) to the DTE. .LP b) \fIc12 \(em Waiting for DIAG (grade 1)\fR .LP In this state, the DCE expects to receive the DIAG element which has as its value the acceptability or not of the DCE identity. .LP c) \fIc13 \(em DCE Identification successful (grade 1)\fR .LP In this state, the DCE has completed its identification successfully. The DCE remains in this state until the switched connection is disconnected. .LP d) \fIc14 \(em DCE Identification unsuccessful (grade 1)\fR .LP The DCE enters this state when the DCE identification attempt has failed. The DCE remains in this state until the switched connection is disconnected. .PP Figure A\(hy2/X.32 provides the state diagram for the DCE acting as the challenged party in the case of security grade\ 1 identification. .PP The actions to be taken by the DCE as the challenged party for security grade\ 1 identification, when one of the listed events occurs, are indicated in Table\ A\(hy2/X.32. .bp .RT .LP .rs .sp 24P .ad r \fBFigure A\(hy2/X.32, p.\fR .sp 1P .RT .ad b .RT .ce \fBH.T. [T10.32]\fR .ce TABLE\ A\(hy2/X.32 .ce \fBActions taken by the DCE as the challenged party (security .ce grade\ 1)\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; lw(60p) | cw(42p) | cw(42p) | cw(42p) | cw(42p) . T{ State of the DCE acting as the challenged party \| \ \| \ Protocol element received by the DCE or decision by the DCE T} T{ \ \| \ \| c11 Initial challenged (grade\ 1) T} T{ \ \| \ \| c12 Waiting for DIAG (grade\ 1) T} T{ \ \| \ \| c13 Identification successful (grade\ 1) T} T{ \ \| \ \| c14 Identification unsuccessful (grade\ 1) (see Note\ 1) T} _ .T& lw(60p) | lw(42p) | lw(42p) | lw(42p) | lw(42p) . T{ DCE decides it wants to be identified T} ID [,\ SIG] \(rac12 T{ //////////////// //////////////// T} T{ //////////////// //////////////// T} T{ //////////////// //////////////// T} _ .T& lw(60p) | cw(42p) | cw(42p) | cw(42p) | cw(42p) . Positive DIAG T{ NORMAL \(rac13 or c14 (see Note\ 2) T} NORMAL \(rac13 DISCARD \(rac13 DISCARD \(rac14 _ .T& lw(60p) | cw(42p) | cw(42p) | cw(42p) | cw(42p) . Negative DIAG NORMAL \(rac14 NORMAL \(rac14 DISCARD \(rac13 T{ DISCARD \(rac14 \fINote\ 1\fR \ \(em\ In this state, the DCE shall disconnect the switched access path. .parag \fINote\ 2\fR \ \(em\ c13 or c14 depending on whether or not the DCE wants to be identified. .parag T} _ .TE .nr PS 9 .RT .ad r \fBTable A\(hy2/X.32 [T10.32], p.\fR .sp 1P .RT .ad b .RT .LP .bp .sp 2P .LP A.3 \fISecurity grade 2 identification\fR .sp 1P .RT .sp 1P .LP A.3.1 \fIDCE acting as the questioning party\fR .sp 9p .RT .PP The DCE acts as the questioning party for security grade 2 when it offers \fIidentified\fR \| or \fIcustomized\fR \| DTE service via the XID or registration DTE identification method with grade\ 2 authentication. Six states are defined for describing the procedures the DCE uses: .RT .LP a) \fIq21 \(em Waiting for ID [, SIG] (grade 2)\fR .LP This is the initial state of the DTE identification process. It is entered after the switched connection is established and, when the registration procedure DTE identification method is used, after the link layer is set up. In this state, the DCE expects to receive the ID (and possibly SIG) element(s) from the DTE. .LP b) \fIq22 \(em Evaluating ID [, SIG] (grade 2)\fR .LP In this state, the DCE begins determining whether or not the DTE identity that was presented in the ID (and possibly SIG) element(s) is acceptable. If the DTE identity is acceptable or the acceptability is not fully determined in this state, the DCE generates the value for the RAND element and transmits it to .LP the DTE. If the DTE identity is unacceptable, the DCE transmits to the DTE the DIAG element with a negative value. .LP c) \fIq23 \(em Waiting for SRES\fR .LP In this state, the DCE expects to receive the SRES element from the DTE. The DCE may continue to evaluate the ID (and possibly SIG) element(s) and, if the DTE identity is unacceptable, the DCE transmits to the DTE the DIAG element with a negative value. .LP d) \fIq24 \(em Evaluating SRES\fR .LP In this state, the DCE determines if the value presented in the SRES element is correct for the DTE identity. If the evaluation of the ID [,\ SIG] element(s) has not already been completed, it is completed in this state. The results of the SRES check (and the last of the ID [,\ SIG] check) is transmitted by the DCE to the DTE as the value of the DIAG element. .LP e) \fIq25 \(em DTE identification successful (grade 2)\fR .LP In this state, the DCE provides the \fIidentified\fR \| or \fIcustomized\fR \| DTE service to the identified DTE. The DCE remains in this state until the switched connection is disconnected. .LP f ) \fIq26 \(em DTE identification unsuccessful (grade 2)\fR .LP In this state, the DCE does not provide the \fIidentified\fR \| or \fIcustomized\fR \| DTE service (unless NUI is used on a per virtual call basis for the \fIidentified\fR \| DTE service) but may provide the \fInonidentified\fR \| DTE service if it is supported. The DCE remains in this state until the switched connection is disconnected. .PP Figure A\(hy3/X.32 provides a state diagram for the DCE acting as the questioning party in case of security grade\ 2 identification. .PP The actions to be taken by the DCE as the questioning party for security grade\ 2 identification, when one of the listed events occurs, are indicated in Table\ A\(hy3/X.32. .RT .sp 1P .LP A.3.2 \fIDCE acting as the challenged party\fR .sp 9p .RT .PP The DCE acts as the challenged party for security grade 2 when it identifies itself to the DTE via the XID or registration DCE identification method with grade\ 2 authentication. Six states are defined for describing the procedures the DCE uses: .RT .LP a) \fIc21 \(em Initial challenged (grade 2)\fR .LP This is the initial state of the DCE identification process. It is entered after the switched connection is established, and, when the registration procedure DCE identification method is used, after the link layer is set up. In this state, the DCE transmits the ID (and possibly SIG) element(s) to the DTE. .LP b) \fIc22 \(em Waiting for RAND\fR .LP In this state, the DCE expects to receive the RAND element. If the ID (and possible SIG) are not acceptable to the DTE, the DCE may receive the DIAG element with a negative value. .bp .LP c) \fIc23 \(em Calculating SRES\fR .LP Using the value of the RAND element, the DCE calculates the value for the SRES element and transmits it to the DTE. If the DTE has continued to evaluate the ID (and possibly SIG) and determined that it is not acceptable, the DCE may receive the DIAG element with a negative value. .LP d) \fIc24 \(em Waiting for DIAG (grade 2)\fR .LP In this state, the DCE expects to receive the DIAG element which has as its value the acceptability or not of the DCE identity and SRES value. .LP e) \fIc25 \(em DCE identification successful (grade 2)\fR .LP In this state, the DCE has completed its identification successfully. The DCE remains in this state until the switched connection is disconnected. .LP f ) \fIc26 \(em DCE identification unsuccessful (grade 2)\fR .LP The DCE enters this state when the DCE identification attempt has failed. The DCE remains in this state until the switched connection is disconnected. .LP .rs .sp 35P .ad r \fBFigure A\(hy3/X.32, p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [T11.32]\fR .ce TABLE\ A\(hy3/X.32 .ce \fBActions taken by the DCE as the questioning party .ce \fB(security grade\ 2)\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) . T{ State of the DCE acting as the questioning party \| \ \| \ Protocol element received by the DCE or decision by the DCE T} T{ \ \| \ \| q21 Waiting for ID\ [,\ SIG] (grade\ 2) T} T{ \ \| \ \| q22 Evaluating ID\ [,\ SIG] (grade\ 2) T} T{ \ \| \ \| q23 Waiting for SRES T} T{ \ \| \ \| q24 Evaluating SRES T} T{ \ \| \ \| q25 DTE identification successful (grade\ 2) T} T{ \ \| \ \| q26 DTE identification unsuccessful (grade\ 2) (see Note\ 1) T} _ .T& lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) . ID [,\ SIG] NORMAL \(raq22 DISCARD \(raq22 DISCARD \(raq23 DISCARD \(raq24 DISCARD \(raq25 DISCARD \(raq26 _ .T& lw(48p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) . T{ At least initial DCE checking of the ID\ [,\ SIG] is complete T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ RAND \(raq23 or Negative DIAG \(raq26 (see Note\ 2) T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} _ .T& lw(48p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) . T{ Further DCE checking (if any) of the ID [,\ SIG] is complete T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ NORMAL \(raq23 or Negative DIAG \(raq26 (see Note\ 3) T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} _ .T& lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) . SRES Negative DIAG\(raq26 Negative DIAG\(raq26 NORMAL \(raq24 DISCARD \(raq24 DISCARD \(raq25 DISCARD \(raq26 _ .T& lw(48p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) . T{ DCE checking of the SRES is complete T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ Positive DIAG \(raq25 or Negative DIAG \(raq26 (see Note\ 4) T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// \fINote\ 1\fR \ \(em\ When in this state, the DCE should disconnect the switched access path when it is sure that the DIAG element has been received by the challenged party, or the challenged party is out\(hyof\(hyorder. .parag \fINote\ 2\fR \ \(em\ As negative DIAG is sent if the DCE has detected ID [,\ SIG] as incorrect. RAND is sent if the DCE has detected ID\ [,\ SIG] as correct or if it has not yet checked ID\ [,\ SIG]. .parag \fINote\ 3\fR \ \(em\ After having transmitted RAND, if the DCE detects that the ID [,\ SIG] received when in state q21 was incorrect, it transmits a negative DIAG and goes into state q26. Otherwise, the DCE continues with the normal process of waiting to receive the SRES element. .parag \fINote\ 4\fR \ \(em\ q25 ou q26 depending on whether or not the SRES is recognized as correct by the\ DCE. .parag T} _ .TE .nr PS 9 .RT .ad r \fBTable A\(hy3/X.32 [T11.32], p.\fR .sp 1P .RT .ad b .RT .LP .rs .sp 5P .ad r Blanc .ad b .RT .LP .bp .PP Figure A\(hy4/X.32 provides a state diagram for the DCE acting as the challenging party in case of security grade\ 2 identification. .PP The actions to be taken by the DCE for security grade 2 identification, when one of the listed events occurs, are indicated in Table\ A\(hy4/X.32. .RT .LP .rs .sp 48P .ad r \fBFigure A\(hy4/X.32, p.\fR .sp 1P .RT .ad b .RT .LP .bp .ce \fBH.T. [T12.32]\fR .ce TABLE\ A\(hy4/X.32 .ce \fBActions taken by the DCE as the challenged party .ce (security grade\ 2)\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) . T{ State of the DCE acting as the challenged party \| \ \| \ Protocol element received by the DCE or decision by the DCE T} T{ \ \| \ \| c21 Initial challenged (grade\ 2) T} T{ \ \| \ \| c22 Waiting for RAND T} T{ \ \| \ \| c23 Calculating SRES T} T{ \ \| \ \| c24 Waiting for DIAG (grade\ 2) T} T{ \ \| \ \| c25 DCE Identification successful (grade\ 2) T} T{ \ \| \ \| c26 DCE Identification unsuccessful (grade\ 2) (see Note\ 1) T} _ .T& lw(48p) | cw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) . T{ DCE decides it wants to be identified T} ID [,\ SIG] \(rac22 ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// ///////////// _ .T& lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) . RAND DISCARD \(rac26 NORMAL \(rac23 DISCARD \(rac23 DISCARD \(rac24 DISCARD \(rac25 DISCARD \(rac26 _ .T& lw(48p) | lw(30p) | lw(30p) | cw(30p) | lw(30p) | lw(30p) | lw(30p) . T{ DCE calculation of SRES from RAND is complete T} T{ ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// T} SRES \(rac24 T{ ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// T} T{ ///////////// ///////////// ///////////// T} _ .T& lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) . Positive DIAG DISCARD \(rac26 T{ NORMAL \(rac25 or c26 (see Note\ 2) T} DISCARD \(rac26 NORMAL \(rac25 DISCARD \(rac25 DISCARD \(rac26 _ .T& lw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) . Negative DIAG DISCARD \(rac26 NORMAL \(rac26 NORMAL \(rac26 NORMAL \(rac26 DISCARD \(rac25 T{ DISCARD \(rac26 \fINote\ 1\fR \ \(em\ In this state, the DCE shall disconnect the switched access path. .parag \fINote\ 2\fR \ \(em\ c25 or c26 depending on whether or not the DCE wants to be identified. .parag T} _ .TE .nr PS 9 .RT .ad r \fBTable A\(hy4/X.32 [T12.32], p.\fR .sp 1P .RT .ad b .RT .ce 1000 ANNEX\ B .ce 0 .ce 1000 (to Recommendation X.32) .sp 9p .RT .ce 0 .ce 1000 \fBAbbreviations\fR .sp 1P .RT .ce 0 .LP ADM Asynchronous disconnected mode .sp 1P .RT .LP AVAIL\(hyBAS Available on all networks .LP AVAIL\(hyNS Available and selected by the network .LP AVAIL\(hyOPT Available on some networks .LP AVAIL\(hyRQ Available on some networks and must be requested .LP BA Class of HDLC .LP CSPDN Circuit switched public data network .bp .LP CUSTOM Customized .LP DCE Data circuit\(hyterminating equipment .LP DIAG Diagnostic element .LP DISC Disconnect .LP DM Disconnected mode .LP DNIC Data network identification code .LP DSE Data switching equipment .LP DTE Data terminal equipment .LP FI Format identifier .LP HDLC High\(hylevel data link control .LP HDTM Half\(hyduplex transmission module .LP ID Identity element .LP ISDN Integrated services digital network .LP ISO International organization for standardization .LP k Number of outstanding I frames .LP LAPB Link access procedure B .LP LAPX Link access procedure \(em Half\(hyduplex .LP MT... Parameter... .LP N... Parameter... .LP ND Network default .LP NN National number .LP NTN Network terminal number .LP NUI Network user identification .LP PDN Public data network .LP PSN Public switched network .LP PSPDN Packet switched public data network .LP PSTN Public switched telephone network .LP RAND Random number element .LP REJ Reject .LP RPOA Recognized private operating agency .LP RR Receive ready .LP RSA Rivest, Shamir, Adleman algorithm .LP SABM Set asynchronous balanced mode .LP SABME Set asynchronous balanced mode extended .LP SIG Signature element .LP SRES Signed response element .LP TCC Telephone country code .LP T... Timer... .LP UA Unnumbered acknowledge .LP UTC Coordinated universal time .LP XC Counter... .LP XID Exchange identification (Unnumbered Format) .LP XT... Timer... .bp .ce 1000 APPENDIX\ I .ce 0 .ce 1000 (to Recommendation X.32) .sp 9p .RT .ce 0 .ce 1000 \fBImplementation of LAPX\fR .sp 1P .RT .ce 0 .LP I.1 \fIIntroduction\fR .sp 1P .RT .PP Considerations are given here for defining the signals needed between the HDTM and the LAPB and physical layer modules in implementing LAPX. .RT .sp 1P .LP I.2 \fIControl and status functions\fR .sp 9p .RT .PP The following logical functions describe interactions between LAPB and the HDTM: .RT .LP \(em \fIcontrol [TERM]\fR .LP LAPB has entered the disconnected phase. .LP \(em \fIcontrol [CONCLUDE]\fR .LP LAPB has finished transmitting one or more frames. .LP \(em \fIstatus [OP\(hyT]\fR .LP Enable LAPB to send frames. .LP \(em \fIstatus [INOP\(hyT]\fR .LP Inhibit LAPB from sending frames. .PP If the idle channel state condition detection mechanism of LAPB is not disabled, then the HDTM needs to protect LAPB from the use of idle channel state condition in turning around the line. This protection is done by having the HDTM present constant flags to LAPB except in the \fIHalf\(hyduplex receiving\fR \| state (state\ 3). It may be desirable to define additional logical functions in doing this. .PP The following logical functions describe interactions between the HDTM and the physical layer: .RT .LP \(em \fIcontrol [SEIZE]\fR .LP The HDTM has stopped waiting for data to be received and is waiting to transmit data. .LP \(em \fIcontrol [RELEASE]\fR .LP The HDTM has stopped sending data and is requesting the physical layer to release the right to transmit. .LP \(em \fIcontrol [DISCON]\fR .LP The HDTM is requesting the physical layer to disconnect the physical connection because LAPB is disconnected. .LP \(em \fIstatus [CALLING]\fR .LP The physical connection originated by this DTE/DCE is established. .LP \(em \fIstatus [CALLED]\fR .LP The physical connection originated by the other DTE/DCE is established. .LP \(em \fIstatus [UNCON]\fR .LP There is no physical connection. .LP \(em \fIstatus [XMT]\fR .LP The physical connection is able to transmit data. .LP \(em \fIstatus [REMOTE]\fR .LP This is an optional function used if the physical layer, instead of the HDTM, detects the indication that the remote DTE/DCE accepts the right to transmit (remote is in the \fIHalf\(hyduplex sending\fR \| state). .LP \(em \fIstatus [LOCAL]\fR .LP This is an optional function used if the physical layer, instead of the HDTM, detects the request for change in the direction of transmission that gives the local DTE/DCE the right to transmit (remote is in the \fIWait or receiving\fR \| state). .PP The forms of these interactions are not defined. However, an example of the HDTM physical layer interactions is given in \(sc\(sc\ 5.6.7 and\ 5.6.8. .sp 1P .LP I.3 \fITable of transitions between states\fR .sp 9p .RT .PP Table I\(hy1/X.32 shows the events that cause a state transition and the resulting action(s). This provides a generalized description of operation of the HDTM. .bp .RT .ce \fBH.T. [1T13.32]\fR .ce TABLE\ I\(hy1/X.32 .ce \fBDescription of state transitions\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(42p) | cw(72p) sw(72p) | cw(42p) , ^ | c | c | ^ . Present state Transition name New state Event Action _ .T& cw(42p) | cw(144p) | cw(42p) . 0 Initialize calling DTE/DCE 4 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .T& cw(42p) | cw(144p) | cw(42p) . 0 Initialize called DTE/DCE 2 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .T& cw(42p) | cw(144p) | cw(42p) . 1 Send right to transmit 2 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .T& cw(42p) | cw(144p) | cw(42p) . 1 Disconnect sending DTE/DCE 0 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .T& cw(42p) | cw(144p) | cw(42p) . 2 Receive confirmation 3 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .T& cw(42p) | cw(144p) | cw(42p) . 2 Seize right to transmit 4 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .TE .nr PS 9 .RT .ad r \fBTABLEAU I\(hy1/X.32 [1T13.32], p. 14\fR .sp 1P .RT .ad b .RT .LP .rs .sp 4P .ad r Blanc .ad b .RT .LP .bp .ce \fBH.T. [2T13.32]\fR .ce TABLE\ I\(hy1/X.32 \fI(continued)\fR .ce \fBDescription of state transitions\fR .ps 9 .vs 11 .nr VS 11 .nr PS 9 .TS center box; cw(42p) | cw(72p) sw(72p) | cw(42p) , ^ | c | c | ^ . Present state Transition name \fR New state Event Action _ .T& cw(42p) | cw(144p) | cw(42p) . 3 Receive right to transmit 4 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .T& cw(42p) | cw(144p) | cw(42p) . 3 Receive right to transmit 2 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .T& cw(42p) | cw(144p) | cw(42p) . 3 Disconnect receiving DTE/DCE 0 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .T& cw(42p) | cw(144p) | cw(42p) . 4 Send confirmation 1 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .T& lw(42p) | cw(144p) | cw(42p) . Any Reset from any state 0 .T& lw(42p) | lw(72p) | lw(72p) | lw(42p) . .TE .nr PS 9 .RT .ad r \fBTABLEAU I\(hy1/X.32 [2T13.32], p. 15\fR .sp 1P .RT .ad b .RT .LP .bp .sp 1P .LP I.4 \fIHDTM/physical layer control and status functions expressed in\fR \fIterms applicable to a modem interface\fR .sp 9p .RT .PP Continuing the example of \(sc\ 5.6.7, the HDTM/physical layer logical functions may be described as shown below as they apply to the use of the HDTM with a V\(hyseries modem interface: .RT .LP \(em \fIcontrol [SEIZE]\fR .LP Request turning circuit 105 ON and, if necessary, releasing circuit 103 from binary\ 1 condition. .LP \(em \fIcontrol [RELEASE]\fR .LP Request holding circuit 103 in the binary 1 condition and turning circuit 105 OFF. .LP \(em \fIcontrol [DISCON]\fR .LP Request turning circuit 107 OFF and, if necessary, turning circuit 105 OFF. .LP \(em \fIstatus [CALLING]\fR .LP As the calling DTE/DCE, report circuit 107 ON. .LP \(em \fIstatus [CALLED]\fR .LP As the called DTE/DCE, report circuit 107 ON. .LP \(em \fIstatus [UNCON]\fR .LP Report circuit 107 OFF. .LP \(em \fIstatus [XMT]\fR .LP Report circuit 106 ON. .LP \(em \fIstatus [REMOTE]\fR .LP Report carrier ON. .LP \(em \fIstatus [LOCAL]\fR .LP Report carrier OFF. \v'1P' .ce 1000 APPENDIX\ II .ce 0 .ce 1000 (to Recommendation X.32) .sp 9p .RT .ce 0 .ce 1000 \fBRSA public key algorithm\fR .sp 1P .RT .ce 0 .PP The Rivest, Shamir, Adleman (RSA) algorithm defines a public key cryptography system. Each subscriber to an RSA cryptosystem generates a public modulo key (\fIn\fR ), a public exponential key (\fIe\fR ), and a secret exponential key (\fId\fR ) which conform to certain consistency rules to be subsequently described. The subscriber can publish and disclose its public keys (\fIn\fR , \fIe\fR ) but it will never reveal its secret exponential key (\fId\fR ). The exchange of information via the RSA algorithm involves the successive .sp 1P .RT .LP transformations and decryption. The form of encryption and decryption transformations are mathematically identical but differ only in the values of the exponential keys used. Each RSA transformation is of the form: \v'6p' .sp 1P .ce 1000 \fIX\fR ` = \fIX\fR \u\fIk\fR\d(modulo \fIn\fR ) .ce 0 .sp 1P .LP .sp 1 where .LP \fIX\fR is the integer to be transformed .LP \fIX\fR ` is the transformed integer .LP \fIn\fR is the public modulo key .LP \fIk\fR is the exponential key which is either the public exponential key \fIe\fR , or the secret exponential key \fId\fR . .PP The RSA keys for a subscriber are generated subject to the following two constraints: .LP \fIn\fR \ =\ \fIp\fR \|\(mu\|\fIq\fR (\fIp\fR and \fIq\fR are large prime numbers) .LP (\fId\fR \|\(mu\|\fIe\fR ) modulo [(\fIp\fR \ \(em\ 1)\|\(mu\|(\fIq\fR \ \(em\ 1)] = 1 .PP The encryption operation can use either \fIe\fR or \fId\fR as the exponential key. However, the decryption operation must use the exponential key .PP (\fId\fR or \fIe\fR ) that was \fInot\fR \| used in the encryption process. Both processes must use the same modulo key, \fIn\fR . .PP As applied to the security grade 2 identification process described in \(sc\ 7.1.2, the challenged party will generate SRES by encrypting RAND using its secret exponential key, \fId\fR , so that the questioning party can decrypt SRES using the public keys of the challenged party (\fIe\fR and\ \fIn\fR ). .bp .RT .ce 1000 APPENDIX\ III .ce 0 .ce 1000 (to Recommendation X.32) .sp 9p .RT .ce 0 .ce 1000 \fBRelationship of timer T14 to the different\fR .sp 1P .RT .ce 0 .ce 1000 \fBmethods of DTE identification\fR .ce 0 .PP Figure III\(hy1/X.32 illustrates the points in the general sequence of events defined in this Recommendation at which timer T14 is started or stopped. .sp 1P .RT .LP .rs .sp 44P .ad r \fBFIGURE III\(hy1/X.32, p. 16\fR .sp 1P .RT .ad b .RT .LP .bp .LP \fBMONTAGE : PAGE 540 = PAGE BLANCHE\fR .sp 1P .RT .LP .bp 
