RSA Security 5.2.2 manual Setting The Algorithm Object

MultiPrime

B_CreateAlgorithmObject:

B_ALGORITHM_OBJ digitalSigner = (B_ALGORITHM_OBJ)NULL_PTR;

if ((status = B_CreateAlgorithmObject (&digitalSigner)) != 0) break;

Step 2: Setting The Algorithm Object

Crypto-C provides three methods for computing RSA digital signatures: MD2 with RSA encryption, MD5 with RSA encryption, and SHA1 with RSA encryption.

Note: Recent cryptanalytic work has discovered a collision in MD2’s internal compression function, and there is some chance that the attack on MD2 may be extended to the full hash function. The same attack applies to MD. Another attack has been applied to the compression function on MD5, though this has yet to be extended to the full MD5. RSA Security recommends that before you use MD, MD2, or MD5, you should consult the RSA Laboratories Web site to be sure that their use is consistent with the latest information.

For this example, choose AI_SHA1WithRSAEncryption. The Reference Manual Chapter 2 entry on this AI states that the format of info supplied to B_SetAlgorithmInfo is NULL_PTR:

if ((status = B_SetAlgorithmInfo

(digitalSigner, AI_SHA1WithRSAEncryption, NULL_PTR)) != 0) break;

Step 3: Init

Associate a key and algorithm method with the algorithm object through B_SignInit. The Reference Manual Chapter 4 entry for this function shows that it takes four arguments: the algorithm object, a key object, an algorithm chooser, and a surrender context. The algorithm object in this example is digitalSigner. Remember, if the algorithm object was not set to AI_MD5WithRSAEncryption, AI_MD2WithRSAEncryption, AI_SHA1WithRSAEncryption, or their BER counterparts, you cannot use B_SignInit. For a key object, use an RSA private key. Follow Steps 1 through 5 of “Generating a Key Pair” on page 214 to produce a key pair. Remember, the modulus must be at least 368 bits.

Build an algorithm chooser with the AMs listed in the Reference Manual Chapter 2

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