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Information about Cmea (cipher)

CMEA
General
James A. Reeds III
1991
Cipher detail
Key size(s):| 64 bits
Block size(s):| 16-64 bits
3
Best public cryptanalysis|-| colspan=2 | 338 chosen plaintexts break all block sizes, 40-80 known plaintexts break 24-bit blocks, and 4 known plaintexts break 16-bit blocks
In cryptography, the Cellular Message Encryption Algorithm (CMEA) is a block cipher which was used for securing mobile phones in the United States. CMEA is one of four cryptographic primitives specified in a Telecommunications Industry Association (TIA) standard, and is designed to encrypt the control channel, rather than the voice data. In 1997, a group of cryptographers (Wagner et al., 1997) published attacks on the cipher showing it had several weaknesses. Some accusations were made that the NSA had pressured the original designers into crippling CMEA, but the NSA has denied any role in the design or selection of the algorithm. The ECMEA and SCEMA ciphers are derived from CMEA.

CMEA is described in U.S. Patent 5,159,634 . It is byte-oriented, with variable block size, typically 2 to 6 bytes. The key size is only 64 bits. Both of these are unusually small for a modern cipher. The algorithm consists of only 3 passes over the data: a non-linear left-to-right diffusion operation, an unkeyed linear mixing, and another non-linear diffusion that is in fact the inverse of the first. The non-linear operations use a keyed lookup table called the T-box, which uses an unkeyed lookup table called the CaveTable. The algorithm is self-inverse; re-encrypting the ciphertext with the same key is equivalent to decrypting it.

CMEA is severely insecure. There is a chosen-plaintext attack, effective for all block sizes, using 338 chosen plaintexts. For 3-byte blocks (typically used to encrypt each dialled digit), there is a known-plaintext attack using 40 to 80 known plaintexts. For 2-byte blocks, 4 known plaintexts suffice.

See also

References

  • David Wagner, Bruce Schneier, John Kelsey (August 1997). "Cryptanalysis of the Cellular Message Encryption Algorithm" (PDF/PostScript). Advances in Cryptology - CRYPTO '97, 17th Annual International Cryptology Conference: pp.526–537. Retrieved on 2007-02-07.CRYPTO%20%2797,%2017th%20Annual%20International%20Cryptology%20Conference&rft.atitle=Cryptanalysis%20of%20the%20Cellular%20Message%20Encryption%20Algorithm&rft.au=David%20Wagner,%20Bruce%20Schneier,%20John%20Kelsey%20%28cryptanalyst%29%7CJohn%20Kelsey&rft.date=August%201997&rft.place=Santa%20Barbara,%20California&rft.pages=pp.526%26ndash%3B537&rft_id=http%3A%2F%2Fwww.schneier.com%2Fpaper-cmea.html"> 

External links

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Cryptography
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History of cryptography | Cryptanalysis | | Topics in cryptography
Symmetric-key algorithm | Block cipher | Stream cipher | Public-key cryptography | Cryptographic hash function | Message authentication code | Random numbers
In cryptography, the key size (alternatively key length) is the size of the digits used to create an encrypted text; it is therefore also a measure of the number of possible keys which can be used in a cipher, and the number of keys which must be tested to 'break' the
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block size. Both the input (plaintext) and output (ciphertext) are the same length; the output cannot be shorter than the input — this is logically required by the Pigeonhole principle and the fact that the cipher must be invertible — and it is simply undesirable for
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Cryptanalysis (from the Greek kryptós, "hidden", and analýein, "to loosen" or "to untie") is the study of methods for obtaining the meaning of encrypted information, without access to the secret information which is normally required to do so.
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Cryptography (or cryptology; derived from Greek κρυπτός kryptós "hidden," and the verb γράφω gráfo "write" or λεγειν legein
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block cipher is a symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. When encrypting, a block cipher might take a (for example) 128-bit block of plaintext as input, and output a corresponding 128-bit block
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mobile phone or cell phone is a long-range, portable electronic device used for mobile communication. In addition to the standard voice function of a telephone, current mobile phones can support many additional services such as SMS for text messaging, email, packet switching
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Motto
"In God We Trust"   (since 1956)
"E Pluribus Unum"   ("From Many, One"; Latin, traditional)
Anthem
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The Telecommunications Industry Association (TIA) is a trade association in the US that represents about 600 telecommunications companies. The TIA will coproduce NXTcomm, a trade show for the telecommunications industry that replaces TIA's GLOBALCOMM (formerly SUPERCOMM) and
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encryption is the process of transforming information (referred to as plaintext) to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key.
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20th century - 21st century
1960s  1970s  1980s  - 1990s -  2000s  2010s  2020s
1994 1995 1996 - 1997 - 1998 1999 2000

Year 1997 (MCMXCVII
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National Security Agency/Central Security Service (NSA/CSS) is the United States government's cryptologic organization that was officially established on November 4, 1952. Responsible for the collection and analysis of foreign communications, it coordinates, directs, and performs
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A schema (pl. schemata), in psychology and cognitive science, is a mental structure that represents some aspect of the world. People use schemata to organize current knowledge and provide a framework for future understanding.
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Byte orientation refers to forms of data processing in which digital data are procesed bytewise. For example, communication is called byte oriented or character oriented when the transmitted information is grouped into bytes.
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block size. Both the input (plaintext) and output (ciphertext) are the same length; the output cannot be shorter than the input — this is logically required by the Pigeonhole principle and the fact that the cipher must be invertible — and it is simply undesirable for
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In cryptography, the key size (alternatively key length) is the size of the digits used to create an encrypted text; it is therefore also a measure of the number of possible keys which can be used in a cipher, and the number of keys which must be tested to 'break' the
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A chosen-plaintext attack (CPA) is an attack model for cryptanalysis which presumes that the attacker has the capability to choose arbitrary plaintexts to be encrypted and obtain the corresponding ciphertexts.
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The known-plaintext attack (KPA) is an attack model for cryptanalysis where the attacker has samples of both the plaintext and its encrypted version (ciphertext) and is at liberty to make use of them to reveal further secret information; typically this is the secret key.
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For the animal, see Oryx.
ORYX is an encryption algorithm used in cellular communications. It is a stream cypher.

External links

  • Cryptanalysis of ORYX
For the helicopter, see Atlas Oryx.

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David A. Wagner (1974) is an Associate Professor of Computer Science at the University of California, Berkeley and a well-known researcher in cryptography and computer security.
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Bruce Schneier

Born 15 January 1963 (1963--) (age 44)

Residence U.S.
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John Kelsey is a cryptographer currently working at NIST. His research interests include cryptanalysis and design of symmetric cryptography primitives (block ciphers, stream ciphers, cryptographic hash functions, MACs), analysis and design of cryptographic protocols, cryptographic
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Portable Document Format (PDF)

Adobe Reader displaying a PDF in Microsoft Windows Vista
File extension: .pdf
MIME type: application/pdf
Type code: 'PDF ' (including a single space)
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For the page description language, see .


A postscript (from post scriptum, a Latin expression meaning "after writing" and abbreviated P.S.
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crypto-, from the Greek kryptos, is an English prefix that means "hidden" or "secret".

The term crypto is also employed as shorthand for the following:
  • Cryptography, the practice of the use of encryption.

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crypto-, from the Greek kryptos, is an English prefix that means "hidden" or "secret".

The term crypto is also employed as shorthand for the following:
  • Cryptography, the practice of the use of encryption.

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block cipher is a symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. When encrypting, a block cipher might take a (for example) 128-bit block of plaintext as input, and output a corresponding 128-bit block
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3-Way

General
Joan Daemen
1994

NOEKEON
BaseKing

Cipher detail
Key size(s):| 96 bits

Block size(s):| 96 bits
Substitution-permutation network
11
Best public cryptanalysis|-| colspan=2 | related-key attack

In cryptography,
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AES
The SubBytes step, one of four stages in a round of AES

General
Vincent Rijmen, Joan Daemen
1998

Square
Anubis, Grand Cru

AES winner, CRYPTREC, NESSIE
Cipher detail
Key size(s):| 128, 192 or 256 bits[1]
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Akelarre

General
G. Álvarez, D. de la Guía, F. Montoya, A. Peinado
1996

IDEA, RC5

Cipher detail
Key size(s):| 128 bits

Block size(s):| 128 bits
Substitution-permutation network
4
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Anubis

General
Vincent Rijmen and Paulo S. L. M. Barreto
2000

Rijndael

Cipher detail
Key size(s):| 128 to 320 bits in steps of 32 bits

Block size(s):| 128 bits
substitution-permutation network
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