Code: Select all
private void cipher(byte[] buffer, int offset, int count, long streamPos)
{
//find block number
var blockSizeInByte = aes.BlockSize / 8;
var blockNumber = (streamPos / blockSizeInByte) + 1;
var keyPos = streamPos % blockSizeInByte;
//buffer
var outBuffer = new byte[blockSizeInByte];
var nonce = new byte[blockSizeInByte];
var init = false;
for (int i = offset; i < count; i++)
{
//encrypt the nonce to form next xor buffer (unique key)
if (!init || (keyPos % blockSizeInByte) == 0)
{
BitConverter.GetBytes(blockNumber).CopyTo(nonce, 0);
encryptor.TransformBlock(nonce, 0, nonce.Length, outBuffer, 0);
if (init) keyPos = 0;
init = true;
blockNumber++;
}
buffer[i] ^= outBuffer[keyPos]; //simple XOR with generated unique key
keyPos++;
}
}
its generating a xor key 16 bytes at a time starting with 1 going to x number and ending at 0.
and here is a quick example
Code: Select all
# py 3.9
# pip install pycryptodome
# pip install passlib
from Crypto.Cipher import AES
from passlib.utils.pbkdf2 import pbkdf1
from struct import pack_into
password = b'Jr9DW9ksMRv1Lc796mrwv145fXC3L5VcpmKE5VfCuvbrpZGfYwXMpwo9sGkJ54zHse4G7zftpjkhqHHY60O7aQPj4M2ekKMSw094PmXRkN4ftTmDFlYMPmwK8QvhJ20H'
salt = b'Jr9DW9ksMRv1Lc796mrwv145fXC3L5VcpmKE5VfCuvbrpZGfYwXMpwo9sGkJ54zHse4G7zftpjkhqHHY60O7aQPj4M2ekKMSw094PmXRkN4ftTmDFlYMPmwK8QvhJ20H'
key = pbkdf1(password, salt, 100, keylen=16, hash='sha1')
block_key = key[:16]
block_size = 0x2000
nonce = bytearray([0] * (block_size * 16))
aes = AES.new(block_key, mode = AES.MODE_ECB)
for i in range(0,block_size):
pack_into('I', nonce, i * 16, (i + 1) % block_size)
out = aes.encrypt(nonce)
print(out.hex())
Code: Select all
PasswordDeriveBytes pdb = new PasswordDeriveBytes(pwd, salt, "Sha1", 100);
var buffer = pdb.GetBytes(0x10);
var nonce = new byte[0x2000];
var outBuffer = new byte[0x2000];
var aes = new AesManaged();
aes.KeySize = 128;
aes.Mode = CipherMode.ECB;
aes.Padding = PaddingMode.None;
aes.Key = buffer;
aes.IV = buffer;
var encryptor = aes.CreateEncryptor(aes.Key, aes.IV);
var block = 1;
BitConverter.GetBytes(block).CopyTo(nonce, 0);
encryptor.TransformBlock(nonce, 0, nonce.Length, outBuffer, 0);so lets say
buffer is '8e2e1d5a5e3a4a1c7388f6b8d7779d7b'
the key is pushed to outbuffer
the first key block 1 would be
"31 0D 83 A9 D0 C0 10 4F FC ED 31 A7 56 E7 8A 85"
the 2nd key block 2 would be
"12 5F 47 C9 11 0C 35 12 D1 AE 25 EA 15 6C C0 0D"
the third key block 3 would be
"E4 E8 EF A9 4C B1 A2 92 AF 54 F0 E8 A4 88 BF BC"
and it would end on block 0
"FA DB B4 83 B5 DC CC EB 51 1C 3D 28 A3 00 53 3F"
How would this be handled in quickbms?