Ladder-DES

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**Ladder-DES**
Best public cryptanalysis:
Designer(s):	Terry Ritter
First published:	1994-02-22
Derived from:	DES
Related to:	DEAL
Key size(s):	224 bits
Block size(s):	128 bits
Structure:	Nested Feistel network
Rounds:	4
Eli Biham's attacks require 2³⁶ plaintexts

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 224 bits.

In 1997, Eli Biham found two forms of cryptanalysis for Ladder-DES that depend on 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.