Simon (cipher)

Simon

One round of Simon
General
Designers	Ray Beaulieu, Douglas Shors, Jason Smith, Stefan Treatman-Clark, Bryan Weeks, Louis Wingers NSA
First published	2013
Related to	Speck
Cipher detail
Key sizes	64, 72, 96, 128, 144, 192 or 256 bits
Block sizes	32, 48, 64, 96 or 128 bits
Structure	Balanced Feistel network
Rounds	32, 36, 42, 44, 52, 54, 68, 69 or 72 (depending on block and key size)
Speed	7.5 cpb (21.6 without SSE) on Intel Xeon 5640 (Simon128/128)
Best public cryptanalysis
Differential cryptanalysis can break 46 rounds of Simon128/128 with 2125.6 data, 240.6 bytes memory and time complexity of 2125.7 with success rate of 0.632.

Simon is a family of lightweight block ciphers publicly released by the National Security Agency (NSA) in June 2013. Simon has been optimized for performance in hardware implementations, while its sister algorithm, Speck, has been optimized for software implementations.

Description of the cipher

The Simon block cipher is a balanced Feistel cipher with an n-bit word, and therefore the block length is 2n. The key length is a multiple of n by 2, 3, or 4, which is the value m. Therefore, a Simon cipher implementation is denoted as Simon2n/nm. For example, Simon64/128 refers to the cipher operating on a 64-bit plaintext block (n=32) that uses a 128-bit key. The block component of the cipher is uniform between the Simon implementations; however, the key generation logic is dependent on the implementation of 2, 3 or 4 keys.

Simon supports the following combinations of block sizes, key sizes and number of rounds:

Block size (bits)	Key size (bits)	Rounds
32	64	32
48	72	36
	96	36
64	96	42
	128	44
96	96	52
	144	54
128	128	68
	192	69
	256	72

See Also

• Balanced boolean function
• Bent function