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A5/3

Stream cipher used in 3G/UMTS mobile communications based on KASUMI block cipher. More secure replacement for A5/1 and A5/2. Uses 128-bit keys with KASUMI operated in OFB-like mode.

Properties

Property	Value
Category	Stream Ciphers
Sub-category	Stream Cipher
Security status	Not classified
Complexity	Advanced
Inventor	3GPP (3rd Generation Partnership Project)
Year	1999
Origin	Not specified
Source	algorithms/stream/a5.js

Parameters

Parameter	Supported values
Key sizes	16 bytes (128 bits)
Block sizes	1 byte (8 bits) to 2500 bytes (20000 bits)

Security

Status: not classified — treat as unverified.

Known vulnerabilities

Issue	Description	Mitigation
Related-Key Attack on KASUMI	Theoretical attacks on KASUMI, but not practical for A5/3	—

Documentation

• Wikipedia: A5/3
• 3GPP TS 55.216 - A5/3 Specification
• KASUMI Specification

References

• CryptoMobile - KASUMI Reference C Implementation (ETSI/SAGE)
• libosmocore KASUMI Implementation

Test vectors

1 vector ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — A5/3 Educational Test Vector (Simplified Implementation)

Source: Educational implementation test

Field	Value
key	000102030405060708090a0b0c0d0e0f
input	00000000000000000000000000000000
expected	029c029c0480ef93029c02bb0480ef93

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