Problem - Kevin Tafuro

ol = 0;
if (!(ret = (char *)malloc(inl + EVP_CIPHER_CTX_block_size(ctx)))) abort( );
for (i = 0; i < inl / 100; i++) {
if (!EVP_EncryptUpdate(ctx, &ret[ol], &tmp, &data[ol], 100)) abort( );
ol += tmp;
}
if (inl % 100) {
if (!EVP_EncryptUpdate(ctx, &ret[ol], &tmp, &data[ol], inl % 100)) abort( );
ol += tmp;
}
if (!EVP_EncryptFinal_ex(ctx, &ret[ol], &tmp)) abort( );
ol += tmp;
if (rb) *rb = ol;
return ret;
}
Here’s a simple function for decryption that decrypts an entire message at once:
#include
#include
char *decrypt_example(EVP_CIPHER_CTX *ctx, char *ct, int inl) {
/* We're going to null-terminate the plaintext under the assumption that it's
* non-null terminated ASCII text. The null can otherwise be ignored if it
* wasn't necessary, though the length of the result should be passed back in
* such a case.
*/
int ol;
char *pt;
if (!(pt = (char *)malloc(inl + EVP_CIPHER_CTX_block_size(ctx) + 1))) abort( );
EVP_DecryptUpdate(ctx, pt, &ol, ct, inl);
if (!ol) { /* There is no data to decrypt */
free(pt);
return 0;
}
pt[ol] = 0;
return pt;
}
See Also
Recipes 5.16, 5.17
5.23 Setting Up and Using RC4
Problem
You want to use RC4 securely.
This is the Title of the Book, eMatter Edition
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Setting Up and Using RC4 | 233