Labels:text | black and white | font | paper | publication | book | document OCR: 2.1.4 Memory Re d-out Techniques It is usually not practical to read the information stored on a security processor directly out of each single memory cell, except for ROM. The stored data has to be accessed via the memory bus where all data is available at a single location. Microprobing is used to observe the entire bus and record the values in metnory as they are accessed. It is difficult to observe all (usually over 20) data and address bus lines at the same time. Various techniques can be used to get around this problemn. Figure 7: This image shows 9 horizontal bus lines For instance we can repeat the same transaction on a depackaged smartcard processor. A UV laser many times and use only two to four probes to ob- (355 nm, 5 ns) was used to remove small patches of serve various subset ...
