Ladder-DES

Infobox block cipher
name = Ladder-DES


caption =
designers = Terry Ritter
publish date = February 22 1994
derived from = DES
derived to =
related to = DEAL
key size = 224 bits
block size = 128 bits
structure = Nested Feistel network
rounds = 4
cryptanalysis = Eli Biham's attacks require 2³⁶ plaintext-ciphertext pairs

In cryptography, Ladder-DES is a block cipher designed in 1994 by Terry Ritter. It is a 4-round Feistel cipher with a block size of 128 bits, using DES as the round function. It has no actual key schedule, so the total key size is 4×56=224 bits.

In 1997, Eli Biham found two forms of cryptanalysis for Ladder-DES that depend on the birthday paradox; the key is deduced from the presence or absence of "collisions", plaintexts that give equal intermediate values in the encryption process. He presented both a chosen-plaintext attack and a known-plaintext attack; each uses about 2³⁶ plaintexts and 2⁹⁰ work, but the known-plaintext attack requires much more memory.

References

* cite newsgroup
title = Ladder DES
author = Terry Ritter
date = February 22 1994
newsgroup = sci.crypt
id = [e-mail]
url = http://groups.google.com/group/sci.crypt/msg/bda8ad116a7769e2
accessdate = 2007-01-30
* cite conference
author = Eli Biham
title = Cryptanalysis of Ladder-DES
booktitle = 4th International Workshop on Fast Software Encryption (FSE '97)
pages = pp.134–138
publisher = Springer-Verlag
date = 1997
location = Haifa
url = http://www.cs.technion.ac.il/users/wwwb/cgi-bin/tr-get.cgi/1997/CS/CS0890.pdf
format = PDF
accessdate = 2007-01-30