View Full Version : a simple substitution cipher or not?

February 26th, 2010, 10:04

just found kind of substitution cipher type (i am quite sure it is substitution), but as i see, substitution cipher like ROT13 use the ascii hex in that range too (if the range is A..Z, then it still using that ascii hex range). but what i found is using another hex range (from 00 ...).

i.e. input :
ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz

1B 18 19 1E 1F 1C 1D 12 13 10 11 16 17 14 15 0A 0B 08 09 0E 0F 0C 0D 02 03 00 7A 3B 38 39 3E 3F 3C 3D 32 33 30 31 36 37 34 35 2A 2B 28 29 2E 2F 2C 2D 22 23 20

i knew its kind of being read back and forth every 2 sequence, kind of big end<>little end thing. anyone know what cipher is this?

February 26th, 2010, 21:37
If that mapping is constant, then yes, it's just a substitution cipher.

February 26th, 2010, 23:50
i was doubting it'd be a substitution cipher, because the routine used in reading a large file, which is, afaik, would be slowing things down.
and i was right, it turn out that this is just a simple xor. well, my bad. thanks

February 27th, 2010, 10:11
Looks indeed like xor with 'Z' = 0x5A.
This is a substitution cipher, indeed, but of a simple kind.