JOSEKI (cipher)

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The JOSEKI algorithm is actually a pair of related algorithms for the encryption and decryption of secret algorithms stored in firmware. The bootstrap code uses a key stored in non-volatile memory to decrypt the operating system code stored encrypted in ROM.

If the physical device is compromised, the firmware cannot be erased and is subject to reverse-engineering. If the firmware is encrypted and the decryption key has been erased, the code so protected is still secure. JOSEKI is unusual in that the encryption algorithm differs from and cannot be deduced from the decryption algorithm. It is a National Security Agency Type 1 algorithm.

[edit] References

JOSEKI-1, A Bootstrap Procedures, National Security Agency, R21-TECH-0062-92, 7 Oct 92 (US Government Information Classification: Secret)

An Implementer’s Guide to JOSEKI-1: A Bootstrap Procedure, National Security Agency, R21-TECH-013-97, 9 April 1997 (US Government Information Classification: Secret/Releasable)

Enhancements to the JOSEKI-1 Bootstrap Procedure, National Security Agency, R21-TECH-013-98, 8 June 1998 (US Government Information Classification: Secret/Releasable)