用 C 加密的数据的 JavaScript AES 256 解密问题

Question

When I do AES-256 CTR encryption in C using tiny-AES-c library ( https://github.com/kokke/tiny-AES-c ) I unable to decrypt it properly in JavaScript. For JavaScript decryption I'm using library https://github.com/ricmoo/aes-js

After encryption I do base 64 encode and before decryption base 64 decode and that part works fine.

In fields below you can see my C and JavaScript code:

C code

// AES start
struct AES_ctx ctx;
uint8_t enc_buf[32];
uint8_t iv[16] = 
    {0xf0,0xf1,0xf2,0xf3,0xf4,0xf5,0xf6,0xf7,0xf8,0xf9,0xfa,0xfb,0xfc,0xfd,0xfe,0xff};
uint8_t key[32] = 
    {0x60,0x3d,0xeb,0x10,0x15,0xca,0x71,0xbe,0x2b,0x73,0xae,0xf0,0x85,0x7d,0x77,0x81,0x1f,0x35,0x2c,0x07,0x3b,0x61,0x08,0xd7,0x2d,0x98,0x10,0xa3,0x09,0x14,0xdf,0xf4};
uint8_t test_str[32] = { 0, };
uint8_t test_str_size = 32;

AES_init_ctx_iv(&ctx, key, iv);

for (unsigned int i = 0; i < test_str_size; i++) {
    test_str[i] = 'A';
}

for (unsigned int i = 0; i < test_str_size / 32; i++) {
    memcpy(enc_buf, test_str + i * 32, 32);
    AES_CTR_xcrypt_buffer(&ctx, enc_buf, 32);
}
// AES end

JavaScript

var key = [96,61,235,16,21,202,113,190,43,115,174,240,133,125,119,129,31,53,44,7,59,97,8,215,45,152,16,163,9,20,223,244];

var encryptedBytes = aesjs.utils.hex.toBytes(ascii_to_hexa(parsedStr));
var aesCtr = new aesjs.ModeOfOperation.ctr(key, new aesjs.Counter(240));
var decrypted = aesCtr.decrypt(encryptedBytes);
console.log('%c AES decrypted: ', 'color: blue', decrypted.toString());

I'm unable to decrypt original data.

Does anyone can help me with this problem? Is there any libraries that is known to be compatible between C and JavaScript?

Thank you in advance.

Answer 1

You need to pass entire IV as initial counter value:

var key = [0x60,0x3d,0xeb,0x10,0x15,0xca,0x71,0xbe,0x2b,0x73,0xae,0xf0,0x85,0x7d,0x77,0x81,0x1f,0x35,0x2c,0x07,0x3b,0x61,0x08,0xd7,0x2d,0x98,0x10,0xa3,0x09,0x14,0xdf,0xf4];
var iv = [0xf0,0xf1,0xf2,0xf3,0xf4,0xf5,0xf6,0xf7,0xf8,0xf9,0xfa,0xfb,0xfc,0xfd,0xfe,0xff];
var parsedStr = '4a9e3cb0185657721fdbca54892184431b2f28dc122058471572c77dce243ad5';

var encryptedBytes = aesjs.utils.hex.toBytes(parsedStr);
var aesCtr = new aesjs.ModeOfOperation.ctr(key, iv);
var decrypted = aesCtr.decrypt(encryptedBytes);
console.log('%c AES decrypted: ', 'color: blue', decrypted.toString());

Output:

[Log]  AES decrypted:  – "65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65,65" (_display, line 40)

Note that it would automatically create aesjs.Counter from the given value if you don't pass an object of aesjs.Counter type. It is equivalent to passing new aesjs.Counter(iv) .

Also note you shouldn't reuse IV for CTR mode. It is supposed to be a random nonce for each packet, so no known plaintext attack is possible.