About: A5/2

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A5/2 is a stream cipher used to provide voice privacy in the GSM cellular telephone protocol. It was designed in 1992-1993 (finished March 1993) as a replacement for the relatively stronger (but still weak) A5/1, to allow the GSM standard to be exported to countries "with restrictions on the import of products with cryptographic security features". The cipher is based on a combination of four linear-feedback shift registers with irregular clocking and a non-linear combiner.

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  • A5/2 is a stream cipher used to provide voice privacy in the GSM cellular telephone protocol. It was designed in 1992-1993 (finished March 1993) as a replacement for the relatively stronger (but still weak) A5/1, to allow the GSM standard to be exported to countries "with restrictions on the import of products with cryptographic security features". The cipher is based on a combination of four linear-feedback shift registers with irregular clocking and a non-linear combiner. In 1999, Ian Goldberg and David A. Wagner cryptanalyzed A5/2 in the same month it was reverse engineered, and showed that it was extremely weak – so much so that low end equipment can probably break it in real time. In 2003, Elad Barkan, Eli Biham and Nathan Keller presented a ciphertext-only attack based on the error correcting codes used in GSM communication. They also demonstrated a vulnerability in the GSM protocols that allows a man-in-the-middle attack to work whenever the mobile phone supports A5/2, regardless of whether it was actually being used. Since July 1, 2006, the GSMA (GSM Association) mandated that GSM Mobile Phones will not support the A5/2 Cipher any longer, due to its weakness, and the fact that A5/1 is deemed mandatory by the 3GPP association. In July 2007, the 3GPP has approved a change request to prohibit the implementation of A5/2 in any new mobile phones, stating: "It is mandatory for A5/1 and non encrypted mode to be implemented in mobile stations. It is prohibited to implement A5/2 in mobile stations." If the network does not support A5/1 then an unencrypted connection can be used. (en)
  • A5/2 est un algorithme de chiffrement par flot utilisé dans le cadre des communications GSM en dehors de l'Europe. Il est basé sur la combinaison non-linéaire de quatre registres à décalage à rétroaction linéaire (LFSR). (fr)
  • In crittografia l'A5/2 è un cifrario a flusso usato per cifrare le comunicazioni vocali effettuate con i telefoni cellulari GSM. Il cifrario è basato su una combinazione di quattro registri a scorrimento LFSR con temporizzazione irregolare ed un combinatore non lineare. L'A5/2 deriva dall'A5/1 ed è stato sviluppato nel 1989 per alcune regioni asiatiche: era deliberatamente più debole del suo predecessore e fu completamente reingegnerizzato nel 1999. Dal 1º luglio 2006 la GSM Association non supporta più lo standard A5/2. (it)
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  • A5/2 est un algorithme de chiffrement par flot utilisé dans le cadre des communications GSM en dehors de l'Europe. Il est basé sur la combinaison non-linéaire de quatre registres à décalage à rétroaction linéaire (LFSR). (fr)
  • In crittografia l'A5/2 è un cifrario a flusso usato per cifrare le comunicazioni vocali effettuate con i telefoni cellulari GSM. Il cifrario è basato su una combinazione di quattro registri a scorrimento LFSR con temporizzazione irregolare ed un combinatore non lineare. L'A5/2 deriva dall'A5/1 ed è stato sviluppato nel 1989 per alcune regioni asiatiche: era deliberatamente più debole del suo predecessore e fu completamente reingegnerizzato nel 1999. Dal 1º luglio 2006 la GSM Association non supporta più lo standard A5/2. (it)
  • A5/2 is a stream cipher used to provide voice privacy in the GSM cellular telephone protocol. It was designed in 1992-1993 (finished March 1993) as a replacement for the relatively stronger (but still weak) A5/1, to allow the GSM standard to be exported to countries "with restrictions on the import of products with cryptographic security features". The cipher is based on a combination of four linear-feedback shift registers with irregular clocking and a non-linear combiner. (en)
rdfs:label
  • A5/2 (de)
  • A5/2 (en)
  • A5/2 (fr)
  • A5/2 (it)
  • A5/2 (zh)
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