RSA Security 5.2.2 Always destroy objects when you no longer need them, DecryptedData = Nullptr

Decrypting the Introductory Example

Step 5: Final

if ((status = B_DecryptFinal

(rc4Decrypter, decryptedData + decryptedLenUpdate, &decryptedLenFinal, encryptedDataLen - decryptedLenUpdate, (B_ALGORITHM_OBJ)NULL_PTR,

(A_SURRENDER_CTX *)NULL_PTR)) != 0) break;

In the “Introductory Example” on page 9, the plaintext was a string. Therefore, we can compute the sum of decryptedLenUpdate and decryptedLenFinal to determine how many characters make up the decryption.

Note: For some algorithms, the decrypted data may not be a string — for example, when the NULL-terminating character was not encrypted. In these cases, if you want to print the decrypted data, you will not be able to because the data is in binary form, not ASCII. You could print the binary data using RSA_PrintBuf(), or you can convert the decrypted data. Crypto-C offers encoding and decoding functions to convert between binary and ASCII. See “Converting Data Between Binary and ASCII” on page 172 for more information.

Step 6: Destroy

Always destroy objects when you no longer need them:

B_DestroyAlgorithmObject (&rc4Decrypter);

if (decryptedData != NULL_PTR) {

T_memset (decryptedData, 0, encryptedDataLen); T_free (decryptedData);

decryptedData = NULL_PTR;

}

2 8 R S A B S A F E C r y p t o - C D e v e l o p e r ’s G u i d e