HP-UX AAA Server A.08.02.10 Administrator's Guide HP-UX 11i v3 (T1428-90093, November 2013)

• Any secret keys used in the RADIUS server for the generation of pseudonyms cannot be
recovered even if a number of matching permanent identities and pseudonyms are available.
• For any given pseudonym or a number of correlated pseudonyms, it is impossible to recover
the corresponding permanent identity.
• It is impossible to determine whether two pseudonyms correspond to the same permanent
identity.
• It is impossible to generate a valid pseudonym irrespective of the underlying permanent identity,
thereby avoiding random forgery.
• It is impossible to generate a valid pseudonym corresponding to a given permanent identity,
thereby avoiding targeted forgery.
To use algorithm-based pseudonyms, the global configuration in the aatv.SIMAKA{} block must
specify one or more Pseudonym-Algorithm-Key-n parameters. The key number specified in
the Pseudonym-Algorithm-Current-Key field is used to encrypt new pseudonyms. The other
keys are used for decryption of pseudonyms generated earlier by them, but are not used for
generation of new pseudonyms. With the algorithm-based pseudonyms, there is no lifetime applied
to the pseudonym. A lifetime can be approximated by defining a new key and making the new
key current. After the desired lifetime, the old key can be removed and the pseudonyms generated
with it are disabled.
While generating a pseudonym based on a permanent identity, an IMSI, the server uses a minor
modification of an algorithm developed by Ericsson2 and submitted to the 3GPP TSG SA WG3
working group. In this case, the pseudonym user name is 24 characters long.
While generating a pseudonym based on a permanent identity, which is a generic user name, for
example, fred, the server uses an algorithm derived from the same Ericsson algorithm. In this case,
the length of the pseudonym varies, depending on the length of the permanent identity, as follows:
• 24 characters, if the permanent user name is 1-8 characters.
• 45 characters, if the permanent user name is 9-24 characters.
• 66 characters, if the permanent user name is 25-40 characters.
• 88 characters, if the permanent user name is 41-56 characters.
• 109 characters, if the permanent user name is 57-72 characters.
• 130 characters, if the permanent user name is 73-88 characters.
• 152 characters, if the permanent user name is 89-104 characters.
• 173 characters, if the permanent user name is 104-120 characters.
• 194 characters, if the permanent user name is 121-136 characters.
• 216 characters, if the permanent user name is 137-152 characters.
• 237 characters, if the permanent user name is 153-168 characters.
NOTE: The pseudonym is not generated if the permanent user name is greater than 168
characters, as the pseudonym identity exceeds 253 characters.
The server generates a pseudonym identity only if the length of the pseudonym@realrealm
string does not exceed 253 characters.
For a given IMSI permanent identity, there are 56 random user bits involved in the pseudonym
generation, resulting in over seven million trillion (7*10
18
) different pseudonyms for a given IMSI.
The probability of a random forgery involving a random IMSI is less than one in four million.
For a given non-IMSI permanent identity, there are 32 random user bits involved in the pseudonym
generation, resulting in over 4 billion different pseudonyms for a given user. The probability of a
random forgery involving a generic user name is less than one in 50 million.
186 Configuring EAP-SIM and EAP-AKA Authentication Methods