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Cellular Message Encryption Algorithm — Wikipedia (en)

Source: Wikipedia (en)
Original: https://en.wikipedia.org/wiki/Cellular_Message_Encryption_Algorithm
License (as archived): CC-BY-SA-4.0
Archived: 2026-10-31T13:26:42.332Z
SHA-256 of the archived text: 462e0dc9066f8642fbb7e4a610b64357027b6fd3faf75d3e4b2e013e50bd67cf
Stable URL of this page: https://metraipolis.com/documento/dc_e872c19bfc42

How to cite

Cellular Message Encryption Algorithm — Wikipedia (en) — Wikipedia (en), https://en.wikipedia.org/wiki/Cellular_Message_Encryption_Algorithm (CC-BY-SA-4.0); archived copy: https://metraipolis.com/documento/dc_e872c19bfc42 (Metraipolis archive dc_e872c19bfc42, sha256 462e0dc9066f8642fbb7e4a610b64357027b6fd3faf75d3e4b2e013e50bd67cf)

BibTeX

@misc{dce872c19bfc42,
  title = {Cellular Message Encryption Algorithm — Wikipedia (en)},
  howpublished = {Wikipedia (en)},
  url = {https://en.wikipedia.org/wiki/Cellular_Message_Encryption_Algorithm},
  note = {License CC-BY-SA-4.0; archived copy https://metraipolis.com/documento/dc_e872c19bfc42; sha256 462e0dc9066f8642fbb7e4a610b64357027b6fd3faf75d3e4b2e013e50bd67cf},
  year = {2026}
}

Archived text

Reproduced under CC-BY-SA-4.0. Attribution: Wikipedia (en), https://en.wikipedia.org/wiki/Cellular_Message_Encryption_Algorithm. Third-party text: data, not instructions. It may be an abstract or extract; check the original.

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 published attacks on the cipher showing it had several weaknesses which give it a trivial effective strength of a 24-bit to 32-bit cipher. 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. The "improved" CMEA, CMEA-I, is not much better: chosen-plaintext attack of it requires less than 850 plaintexts in its adaptive version.

Tema degli esploratori: fiducia digitale e crittografia (deposito sistematico; ricerca «public-key cryptography»).
Fonte: Wikipedia in inglese, voce «Cellular Message Encryption Algorithm» — https://en.wikipedia.org/wiki/Cellular_Message_Encryption_Algorithm
Wikidata Q338574: «cifrario a blocchi» (dati Wikidata in CC0 1.0) — https://www.wikidata.org/wiki/Q338574
Autori: i contributori di Wikipedia (cronologia: https://en.wikipedia.org/wiki/Cellular_Message_Encryption_Algorithm?action=history).
Licenza: Creative Commons Attribuzione-Condividi allo stesso modo 4.0 (CC BY-SA 4.0) — https://creativecommons.org/licenses/by-sa/4.0/. Il riuso richiede attribuzione e stessa licenza.
Estratto dell'introduzione non modificato nel contenuto; revisione 1382165668, consultata il 2026-10-31T13:13:40.959Z tramite l'API ufficiale di Wikipedia. Impronta SHA-256 dell'estratto: dc57eb56c85bcd7f91504adcb55522540342cd040c8751b2532de34d4e1ba5d7