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ETSI TETRA TEA
TETRA Authentication Algorithm
TAA or TAA1, the abbreviation of TETRA Authentication Algorithm 1, is a suite
of algorithms, associated with
Terrestrial Trunked Radio (TETRA), a
European standard for public safety and emergency services, standardized
by the European Telecommunications Standards Institute (ETSI) [1].
They are used for authentication, key derivation and Over The Air Re-keying
(OTAR) [3].
The suite consists of cryptographic primitives and non-cryptographic
transformation functions. All cryptographic primitives rely on a proprietary
block cipher known as HURDLE, which was developed in 1996/97 at
Royal Holloway University of London (UK) for ETSI-SAGE.
After evaluation by the other ETSI-SAGE members,
it was submitted as a formal ETSI standard.
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All TETRA-related algorithms are secret and have never been submitted for
peer-review or in-depth security analysis.
In July 2023, Dutch cyber security firm
Midnight Blue revealed that it had
managed to extract, isolate, reconstruct and analyse the TAA, TEA1,
TEA2 and TEA3 algorithms from a working TETRA radio as part of
its RE:TETRA and
TETRA:BURST research projects.
Five vulnerabilities were found, two of which were deemed
critical [2]. A slightly less critical flaw was found in the TAA
algorithm, which leads to a weak anonymization [2][3].
HURDLE is a balanced 16-round Feistel network with a 128-bit key and a
64-bit block size. Each round key — 96 bits are used per round — is derived
from its predecessor, through a simple linear function that wraps around
in 16 rounds. For a more complete description, check out [3].
➤ Read the paper
➤ More about TETRA:BURST
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© Crypto Museum. Created: Wednesday 09 August 2023. Last changed: Saturday, 12 August 2023 - 13:57 CET.
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