-s[password]   Decrypt files

  This option is used to unscramble (decrypt) the files in a .ZIP file.
  PKZIP has a -s option which is used to encrypt the files.  If a password
  is not specified the user will be prompted for it.  When extracting a .ZIP
  file that has been encrypted, the files will not be extracted unless the
  correct key (password) is included on the command line or entered at the
  prompt.

  Notice there is no space between the -s and the encryption key.

     pkunzip payroll.zip -o -sSecret *.dbf

  In the above example, all files with a "dbf" extension will be extracted
  and the key "Secret" applied to them.  This will only work if the files
  have been compressed with the key of "Secret" applied to them.

  This option is case sensitive.  This means that "Secret", "secret" and
  "SECRET" are all different passwords.