Abstract: A secure cryptographic rights unit for cryptographically regulating access to digital content includes an interface control processor and a specialized cryptographic unit that protects access to a memory. Rights keys, which allow access to content, are added by the cryptographic unit by transforming data received from the control processor and storing the result in the protected memory. The cryptographic unit then produces content decryption keys by using stored rights keys to transform other data received from the control processor. Because the control processor does not have the ability to directly access the protected memory, the security can remain effective even if the control processor is compromised. To prevent reverse engineering of the cryptographic transformations, the invention provides for an algorithm generator that uses random sources to produce algorithm definitions in machine-readable form. Because the generator itself does not contain any secrets, it can be submitted for open review.

Abstract: Methods and apparatuses are disclosed for improving DES and other cryptographic protocols against external monitoring attacks by reducing the amount (and signal-to-noise ratio) of useful information leaked during processing. An improved DES implementation of the invention instead uses two 56-bit keys (K1 and K2) and two 64-bit plaintext messages (M1 and M2), each associated with a permutation (i.e., K1P, K2P and M1P, M2P) such that K1P {K1} XOR K2P {K2} equals the “standard” DES key K, and M1P {M1} XOR M2P {M2} equals the “standard” message. During operation of the device, the tables are preferably periodically updated, by introducing fresh entropy into the tables faster than information leaks out, so that attackers will not be able to obtain the table contents by analysis of measurements. The technique is implementable in cryptographic smartcards, tamper resistant chips, and secure processing systems of all kinds.