# Why length of only 32-bits in 128-EIA3 MAC?

## Why length of only 32-bits in 128-EIA3 MAC?

Typically by today's standards, MACs are of greater length than 32-bits. Having only

32 bits allows birthday-paradox comments like this

(Although the comment there relies on prohibited assumption of the use of one IV twice)

So, why only 32-bit MAC?

**koko**- Guest

## RE: Why length of only 32-bits in 128-EIA3 MAC?

The MAC size is part of the overall LTE standard, and not specific to the ZUC-based algorithm. It's the same for all of 128-EIA1, 128-EIA2 and 128-EIA3.koko wrote:

Typically by today's standards, MACs are of greater length than 32-bits. Having only

32 bits allows birthday-paradox comments like this

(Although the comment there relies on prohibited assumption of the use of one IV twice)

So, why only 32-bit MAC?

Larger MACs mean that messages occupy more bandwidth and take longer to send - i.e. they come at a cost. In the LTE context, where the secret key used for integrity protection does not have a very long lifetime, a 32-bit MAC seems sufficient to give good protection against realistic threats.

**Steve Babbage**- Posts : 30

Join date : 2010-08-02

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