hexHexChars = '0123456789abcdef'
modHexChars = 'cbdefghijklnrtuv'

hex2ModDict = dict(zip(hexHexChars, modHexChars))
mod2HexDict = dict(zip(modHexChars, hexHexChars))

def modhex_encode(s):
    return ''.join(
        [ hex2ModDict[c] for c in s.encode('hex') ]
    )
# end def modhex_encode

def modhex_decode(m):
    return ''.join(
        [ mod2HexDict[c] for c in m ]
    ).decode('hex')
# end def modhex_decode