Is this a known DES cipher? What DES cipher is it? DES-CTR?

import Crypto.Cipher.DES
import stru开发者_运维问答ct

def rol32(x, y):
    ret = ((x<<y)&0xFFFFFFFF)|((x>>(32-y))&0xFFFFFFFF)
    #print 'rol32', hex(x), hex(y), hex(ret)
    return ret
def sub32(x, y):
    ret = (x & 0xFFFFFFFF) - (y & 0xFFFFFFFF)
    if ret < 0: ret += 0x100000000
    #print 'sub32', hex(x), hex(y), hex(ret)
    return ret
def mul32(x, y):
    ret = (x * y) & 0xFFFFFFFF
    #print 'mul32', x, y
    return ret

d = Crypto.Cipher.DES.new('\xcd\x67\x98\xf2\xa4\xb6\x70\x76', Crypto.Cipher.DES.MODE_ECB)

def decrypt(offset, f):
    out_buf = []
    b = f.read(16)
    buf = d.decrypt(b)
    buf = buf[8:] + buf[:8]
    for i in range(0,4):
        val = struct.unpack('<I', buf[i*4:i*4+4])[0]
        val = sub32((sub32(0x8927462, mul32(offset, 0x3210789B)) ^ rol32(val, offset % 32)), 0x12345678)
        tmp = struct.pack('<I', val)
        out_buf.append(ord(tmp[0]))
        out_buf.append(ord(tmp[1]))
        out_buf.append(ord(tmp[2]))
        out_buf.append(ord(tmp[3]))
    for i in range(len(out_buf)-1,len(out_buf)-16,-1):
        out_buf[i] ^= out_buf[i-1]
    out_buf[len(out_buf)-16] ^= (offset & 0xFF) ^ ((offset >> 14) & 0xFF)
    return out_buf

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No. It is certainly not CTR-mode. It looks like a disc encryption mode. In particular the encryption mode has some slight resemblance with LRW. The main idea is to tweak the input depending on the block number, so that encrypting the same block multiple times does not result in the same ciphertext. It allows to re-encrypt a message partially, but an attacker will notice, which parts of the plaintext changes.

Hence there is some small information leakage. Since I also don't see any authentication, I don't think I like this encryption mode.