Problem - Kevin Tafuro

}
RC4_set_key(&k, HASH_SZ, (char *)tmp);
RC4(&k, blklen - HASH_SZ, out + HASH_SZ, out + HASH_SZ);
}
See Also
Recipes 4.10, 5.23, 6.7
5.16 Using a High-Level, Error-Resistant
Encryption and Decryption API
Problem
You want to do encryption or decryption without the hassle of worrying about
choosing an encryption algorithm, performing an integrity check, managing a nonce,
and so on.
Solution
Use the following “Encryption Queue” implementation, which relies on the reference
CWC mode implementation (discussed in Recipe 5.10) and the key derivation
function from Recipe 4.11.
Discussion
Be sure to take into account the fact that functions in this API can fail,
particularly the decryption functions. If a decryption function fails,
you need to fail gracefully. In Recipe 9.12, we discuss many issues that
help ensure robust network communication that we don’t cover here.
This recipe provides an easy-to-use interface to symmetric encryption. The two ends
of communication must set up cipher queues in exactly the same configuration.
Thereafter, they can exchange messages easily until the queues are destroyed.
This code relies on the reference CWC implementation discussed in Recipe 5.10. We
use CWC mode because it gives us both encryption and integrity checking using a
single key with a minimum of fuss.
We add a new data type, SPC_CIPHERQ, which is responsible for keeping track of
queue state. Here’s the declaration of the SPC_CIPHERQ data type:
typedef struct {
cwc_t ctx;
unsigned char nonce[SPC_BLOCK_SZ];
} SPC_CIPHERQ;
Using a High-Level, Error-Resistant Encryption and Decryption API | 217
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