RSA Security 5.2.2 manual Generating an RSA MultiPrime Key, Set the Algorithm Object

MultiPrime

Generating an RSA MultiPrime Key

Refer to the RSA_CreateMultiPrimeRSAKeypair routine defined in the samples/pkalg/ rsa/rsautil.c file for an example that shows the use of AI_RSAMultiPrimeKeyGen to generate an RSA public/private key pair. This routine is called by the rsamultp.c sample.

RSA MultiPrime key generation follows the same steps as standard RSA key pair generation with a couple of exceptions. The differences are that AI_RSAMultiPrimeKeyGen must be used instead of AI_RSAKeyGen. Also, as indicated in the Reference Manual entry for the appropriate AI, the algorithm chooser passed in during the B_GenerateInit call must include AM_RSA_MULTI_PRIME_KEY_GEN.

Step 1: Prepare A_RSA_MULTI_PRIME_KEY_GEN_PARAMS Structure

To use AI_RSAMultiPrimeKeyGen in the call to B_SetAlgorithmInfo, we must first prepare an A_RSA_MULTI_PRIME_KEY_GEN_PARAMS structure, which is defined as follows:

typedef struct { unsigned int modulusBits; unsigned int numberOfPrimes; ITEM publicExponent;

} A_RSA_MULTI_PRIME_KEY_GEN_PARAMS;

The numberOfPrimes field must be set to a value of 2 or more. If it is set to 2, it is equivalent to generating a standard RSA key pair as is the case with AI_RSAKeyGen. If numberOfPrimes is set to 3 or more, the modulusBits field must be at least 1024.

Step 2: Set the Algorithm Object

If we have an algorithm object, keypairGenerator, which has already been created with a call to B_CreateAlgorithmObject, we can then set the algorithm object's info as follows:

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