Synology NAS DS220j: findhost password encode/decode

password-coding.py

import numpy as np

mtrx64 = np.matrix([
        [0.0, 2.0, 2.0, -3.0, 0.0, 1.0, 3.0, -1.0],
        [1.0, 1.0, -2.0, 3.0, -1.0, 0.0, 0.0, 5.0],
        [-2.0, 1.0, 1.0, -1.0, 3.0, 0.0, -1.0, -2.0],
        [-1.0, 0.0, 0.0, 0.0, 2.0, -3.0, -4.0, 1.0],
        [0.0, -2.0, 1.0, 2.0, -2.0, 1.0, -2.0, -1.0],
        [-1.0, 2.0, 0.0, 2.0, -2.0, -2.0, 1.0, 0.0],
        [2.0, -4.0, 3.0, -2.0, 1.0, 5.0, 3.0, 1.0],
        [1.0, 0.0, -5.0, 0.0, -1.0, -2.0, -1.0, -3.0]
    ])
mtri64 = mtrx64.I
mapd2c = b'UPX-BkYa4Fyi2DjcLef6WmOA8pZrshQ+uv7Vwx3G9oHb1EIJKzMg5NqRSCtTld0n'
mapc2d = [0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 
          0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 
          0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x1f, 0x0, 
          0x3, 0x0, 0x0, 0x3e, 0x2c, 0xc, 0x26, 0x8, 0x34, 0x13, 0x22, 0x18, 0x28,
          0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x17, 0x4, 0x39, 0xd, 0x2d, 0x9, 0x27, 
          0x2a, 0x2e, 0x2f, 0x30, 0x10, 0x32, 0x35, 0x16, 0x1, 0x1e, 0x37, 0x38, 0x3b, 
          0x0, 0x23, 0x14, 0x2, 0x6, 0x1a, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x7, 0x2b, 0xf, 
          0x3d, 0x11, 0x12, 0x33, 0x1d, 0xb, 0xe, 0x5, 0x3c, 0x15, 0x3f, 0x29, 0x19, 
          0x36, 0x1b, 0x1c, 0x3a, 0x20, 0x21, 0x24, 0x25, 0xa, 0x31, 0x0, 0x0, 0x0, 0x0, 0x0]

def matrix_encode(password):
    # prepare password matrix
    pwd_aligned_len = (len(password) + 7) & 0x7FF8
    pwd_mtrx = np.zeros( (pwd_aligned_len, 8) )
    for i in range(len(password)):
        pwd_mtrx[i//8][i%8] = password[i]
    # multiply password matrix and const matrix
    out_mtrx = pwd_mtrx.dot(mtrx64)
    #
    out = []
    out_len = 2*(pwd_aligned_len)
    for i in range(out_len):
        el = int(out_mtrx[i//8,i%8])
        out.append(mapd2c[el & 0x3f])
        out.append(mapd2c[(el >> 6) & 0x3f])
    return bytes(out)

def matrix_decode(epassword):
    if len(epassword) & (7<<1) != 0:
        return None
    # prepare password matrix
    epwd_aligned_len = len(epassword) >> 4
    epwd_mtrx = np.zeros( (epwd_aligned_len, 8) )
    for i in range(len(password)//2):
        val = mapc2d[epassword[i*2]]
        val |= mapc2d[epassword[i*2+1]] << 6
        val_flt = float(val) if val & 0x800 else float()
        epwd_mtrx[i//8][i%8] = val_flt
    #
    pwd_mtrx = epwd_mtrx.dot(mtri64)
    out = [int(pwd_mtrx[i//8,i%8] + 0.01)&0xff for i in range(len(epassword)//2)]
    return bytes(out)