# Tag Info

5

No, since finding $a$ allows offline checking of passwords. $\:$ No, although I can't back this part up.

1

The multiplier parameter $k$ is different between SRP 6 and 6a. You can see that RFC 5054 calculates it using a hash of the domain parameters (modulus $N$ and generator $g$), so it is using SRP 6a, as opposed to SRP 6 where $k$ is constant. Likewise, in section 6.2.1 of IEC 11770-4 – the October 2005 draft at least – the equivalent value $c$ is defined as a ...

1

You can pre-compute and hardcode N and g into your client and server. There's no harm in doing this. I do not believe that using per-user N will provide any additional security. It is common practice to define SRP parameters for a particular application or (larger) protocol, see e.g. RFC 5054.

1

Short: SRP. For encrypted key exchange you need to add key confirmation to get challenge-response authentication. These all are password-authenticated key exchange (PAKE) mechanisms. These mechanisms end-up into peers sharing an agreed key, which is only the same if the password agreement was successful. Challenge-response authentication is usually ...

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