| 摘要 |
In accordance with the invention, a postal security device (PSD) ( 10 ) contains a non-volatile memory ( 13 ) which does not depend on battery power such as an EEPROM ( 13 ), and contains a nonvolatile memory ( 14, 16 ) which does depend on battery power, such as a static RAM. The PSD ( 10 ) also contains an encryption engine ( 12, 14, 22 ). An encryption key is developed and is stored in the static RAM ( 14 ), which is sized to be only large enough to contain the encryption key. A large body of data, too large to fit in the static RAM, is encrypted by means of the encryption engine ( 12, 14, 22 ) and with reference to the encryption key, and is stored in the EEPROM ( 13 ). This body of data typically includes cryptographic keys and sensitive bit-images. When the PSD is powered, a large RAM (typically a dynamic RAM) ( 16 ) is available to receive the large body of data, decrypted using the encryption key. A tamper switch ( 17 ) cuts power to both RAMs ( 14, 16 ) in the event of tampering.
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