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- Der CMEA (Cellular Message Encryption Algorithm) ist eine Blockchiffre, welche in amerikanischen Mobilfunksystemen eingesetzt wird und von James A. Reeds 1991 bei AT&T entwickelt wurde. Er ist in US-Patent 5.159.634 patentiert. Er wird verwendet um die Steuerdaten in US-Mobilfunknetzen bei der Funkübertragung zu verschlüsseln und besitzt einen ähnlichen Anwendungsbereich wie der in Europa und in GSM-Mobilfunknetzen verwendete A5-Algorithmus. Der Algorithmus ist byteorientiert und kann mit Blockgrößen zwischen zwei und sechs Bytes arbeiten. Die Schlüssellänge beträgt 64 Bit. CMEA gilt als unsicher. (de)
- 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 and 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. (en)
- Cellular Message Encryption Algorithm (CMEA) est un algorithme de chiffrement par bloc utilisé pour les communications en téléphonie mobile aux États-Unis. CMEA est une des quatre primitives cryptographiques décrites par le (TIA) dès 1992. Les spécifications seront mises à jour en 1995. D'autres algorithmes sont basés sur CMEA : et . Le chiffrement se décompose en trois parties :
* une transformation non linéaire sur le bloc
* une transformation linéaire basée sur un XOR entre les deux parties du bloc
* une transformation non linéaire, inverse de la première CMEA est décrit par la patente US 5,159,634. (fr)
- In crittografia il Cellular Message Encryption Algorithm, abbreviato CMEA, è un cifrario a blocchi che è stato utilizzato per rendere sicuri i telefoni cellulari negli Stati Uniti d'America. Il CMEA è una delle 4 primitive crittografiche specificate in uno standard della Telecommunications Industry Association (TIA): specificatamente, era usato per cifrare il canale di controllo piuttosto che i dati vocali. Nel 1997 un gruppo di crittografi ha pubblicato diversi attacchi al cifrario, dimostrando che aveva diverse vulnerabilità. Sono state anche formulate ipotesi secondo le quali la National Security Agency (NSA) avesse fatto pressioni sugli sviluppatori dell'algoritmo affinché realizzassero un cifrario debole, ma l'NSA ha sempre negato ogni ruolo nella progettazione o nella selezione dell'algoritmo. I cifrari e derivano dal CMEA. (it)
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- 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 and ciphers are derived from CMEA. (en)
- Der CMEA (Cellular Message Encryption Algorithm) ist eine Blockchiffre, welche in amerikanischen Mobilfunksystemen eingesetzt wird und von James A. Reeds 1991 bei AT&T entwickelt wurde. Er ist in US-Patent 5.159.634 patentiert. Er wird verwendet um die Steuerdaten in US-Mobilfunknetzen bei der Funkübertragung zu verschlüsseln und besitzt einen ähnlichen Anwendungsbereich wie der in Europa und in GSM-Mobilfunknetzen verwendete A5-Algorithmus. (de)
- Cellular Message Encryption Algorithm (CMEA) est un algorithme de chiffrement par bloc utilisé pour les communications en téléphonie mobile aux États-Unis. CMEA est une des quatre primitives cryptographiques décrites par le (TIA) dès 1992. Les spécifications seront mises à jour en 1995. D'autres algorithmes sont basés sur CMEA : et . Le chiffrement se décompose en trois parties :
* une transformation non linéaire sur le bloc
* une transformation linéaire basée sur un XOR entre les deux parties du bloc
* une transformation non linéaire, inverse de la première (fr)
- In crittografia il Cellular Message Encryption Algorithm, abbreviato CMEA, è un cifrario a blocchi che è stato utilizzato per rendere sicuri i telefoni cellulari negli Stati Uniti d'America. Il CMEA è una delle 4 primitive crittografiche specificate in uno standard della Telecommunications Industry Association (TIA): specificatamente, era usato per cifrare il canale di controllo piuttosto che i dati vocali. Nel 1997 un gruppo di crittografi ha pubblicato diversi attacchi al cifrario, dimostrando che aveva diverse vulnerabilità. Sono state anche formulate ipotesi secondo le quali la National Security Agency (NSA) avesse fatto pressioni sugli sviluppatori dell'algoritmo affinché realizzassero un cifrario debole, ma l'NSA ha sempre negato ogni ruolo nella progettazione o nella selezione dell' (it)
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- CMEA (de)
- Cellular Message Encryption Algorithm (en)
- CMEA (cryptographie) (fr)
- Cellular Message Encryption Algorithm (it)
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