Block Ciphers
196 RSA BSAFE Crypto-C Developer’s Guide
Decrypting
As in the “Introductory Example” on page 9, decrypting is similar to encrypting. Use
the same AI, IV, and key data. Use the proper decrypting AM and call
B_DecryptInit,
B_DecryptUpdate, and B_DecryptFinal.
The RC6 Cipher
The RC6 cipher was developed by Ronald Rivest and Matthew Robshaw, Ray Sidney,
and Lisa Yin of RSA Laboratories West as a candidate for the Advanced Encryption
Standard (AES). RC6 allows for a variable number of rounds; however, the
implementation in this version of Crypto-C fixes the number of rounds at 20. Later
versions of Crypto-C may extend this value.
The example in this section corresponds to the file
rc6.c, which uses AI_RC6_CBCPad.
AI_FeedbackCipher also supports the RC6 symmetric block cipher.
AI_FeedbackCipher is useful if your application has a need to support block cipher
modes other than CBC. See the
rc6fb.c sample program for more information.
Step 1: Create
Declare a variable to be B_ALGORITHM_OBJ and as defined in the function prototype in
Chapter 4 of the Reference Manual, its address is the argument for
B_CreateAlgorithmObject.
Step 2: Set
For this example, you will perform an RC6 operation in CBC mode using PKCS V#5
padding. To do this, use
AI_RC6_CBCPad in the call to B_SetAlgorithmInfo. Notice
if (encryptedData != NULL_PTR) {
T_memset (encryptedData, 0, encryptedDataLen);
T_free (encryptedData);
encryptedData = NULL_PTR;
}
B_ALGORITHM_OBJ rc6Encrypter = (B_ALGORITHM_OBJ)NULL_PTR;
if ((status = B_CreateAlgorithmObject (&rc6Encrypter)) != 0)
break;
