Discussion about RNG on comments list

All,

maybe you’ve seen the short discussion on CKF_RNG, CKR_RANDOM_NO_RNG and C_GenerateRandom on the pkcs11-comments list.

Then main question is: When is a token allowed to set CKF_RNG? The definition in table 6 of base standard v3.0 says: “True if the token has its own random number generator”. It does not say TRUE random number generator. Was this actually intended?

If this was the intention then CKF_RNG can actually be false but C_GenerateRandom could still return data since “C_GenerateRandom generates random or pseudo-random data” (section 5.19.2). The term “random number generator” is not used here at all.

If CKF_RNG means “any RNG” then GenerateRandom returns CKR_RANDOM_NO_RNG if and only if CKF_RNG == false.

In the 2^nd case the thread started suggested to a new flag really indicating that there is a true RNG. But IMO an application cannot be sure that the TRNG is really used when C_GenerateRandom is called…

BTW: Why is there CKR_RANDOM_NO_RNG at all? Wouldn’t it be enough if C_GenerateRandom returned CKR_FUNCTION_NOT_SUPPORTED? Since C_GenerateRandom does not have a parameter to specify a particular RNG type what’s the difference in the error code? The same holds for C_SeedRandom and CKR_RANDOM_SEED_NOT_SUPPORTED. In fact, the token can have an RNG but only use it for GenerateKey(Pair), but not support C_GenerateRandom. Why is it important to be able to differentiate between “no RNG” and “function not supported” if the result is basically the same – I get no random data?

Best,

Daniel

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