1 Reply by Iguananaut

(3 replies, posted in wolfCrypt)

Sounds good, thanks!

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2 Reply by Iguananaut

(3 replies, posted in wolfCrypt)

Nevermind; a glance at the WolfSSL test suite pointed me in the right direction.  One needs separate Aes structs for encryption and decryption.  Looking at the source code makes it clear why, at least for the native implementation: The counter state is maintained on the Aes struct, so it would have to be reset before decryption (or otherwise, just use a different instance).

Consider this then a bug report against the documentation, which isn't clear about this smile

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3 Topic by Iguananaut

(3 replies, posted in wolfCrypt)

Greetings, and happy new(-ish) year,

I have an application that's using AES in CTR mode, and I've been working with it for quite a while (thankfully not in production yet) just assuming that my encryption was working.  I feel like I've tested it before but it would have been a few weeks ago.  In any case, I was recently doing some verification tests and found that my AES-encrypted data was not being decrypted properly, and now as far as I can tell CTR mode just isn't working properly.  To confirm it wasn't just a problem elsewhere in my code I wrote a simple test program almost exactly following the docs here:

https://www.wolfssl.com/wolfSSL/Docs-wo … i-aes.html (under wc_AesCtrEncrypt).

To be clear, my exact test code is as follows:

#include <wolfssl/options.h>
#include <wolfssl/wolfcrypt/aes.h>
#include <wolfssl/wolfcrypt/types.h>
#include <wolfssl/wolfcrypt/random.h>
#include <stdio.h>

int main(void) {
    byte msg[16] = "abcdefghijklmnop";
    byte cipher[16];
    byte decrypted[16];
    Aes enc_dec;
    RNG rng;
    int idx;

    byte *key = malloc(32);
    byte *iv = malloc(16);

    wc_InitRng(&rng);

    wc_RNG_GenerateBlock(&rng, key, 32);
    wc_RNG_GenerateBlock(&rng, iv, 32);

    if(wc_AesSetKeyDirect(&enc_dec, key, 32, iv, AES_ENCRYPTION) < 0) {
        printf("Error setting key\n");
        return -1;
    }

    wc_AesCtrEncrypt(&enc_dec, cipher, msg, sizeof(msg));
    wc_AesCtrEncrypt(&enc_dec, decrypted, cipher, sizeof(cipher));
    for (idx = 0; idx < 16; idx++) {
        printf("%c", (char)decrypted[idx]);
    }
    printf("\n");
    return 0;
}

I would expect `decrypted` to contain the original message, but instead it just prints gibberish.  Am I missing something obvious?

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