5 ms·

ISAAC (http://burtleburtle.net/bob/rand/isaacafa.html http://burtleburtle.net/bob/rand/isaacafa.html) for a CSPRNG. But what is your use-case for something non-

ISAAC (http://burtleburtle.net/bob/rand/isaacafa.html http://burtleburtle.net/bob/rand/isaacafa.html) for a CSPRNG. But what is your use-case for something non-standard? Just use /dev/urandom

derefr 10y ago
How about, backing the equivalent of /dev/urandom for a unikernel OS?
dchest 10y ago
No, no, no, don't use ISAAC.
- forgotpwtomain 10y ago
  Do you have a citation you can provide? I don't know of any research that has shown a significant weakness in ISAAC.
  - dchest 10y ago
    Why would you use a PRNG with unknown cryptographic properties, not designed by a cryptographer, as opposed to one of the NIST's DRBG or a good stream cipher, such as ChaCha? Weakness: https://eprint.iacr.org/2006/438 https://eprint.iacr.org/2006/438 — "huge subsets of internal states which induce a strongly non-uniform distribution in the 8192 first bits produced" Finally, why is deterministic PRNG suggested as a replacement for OpenSSL's random number generator? In general, the advice to write your own userspace PRNG replacement for OpenSSL is not a good advice, because many people are not competent enough to do it.
    - forgotpwtomain 10y ago
      > as opposed to one of the NIST's DRBG I certainly wouldn't go anywhere near another NIST DRBG.. > https://eprint.iacr.org/2006/438 https://eprint.iacr.org/2006/438 From my brief understanding Aumasson's paper uses a different seeding routine from the example provided in the c implementation which allows the weaker states to be produced - indeed it's mentioned on the author's website. > Finally, why is deterministic PRNG suggested as a replacement for OpenSSL's random number generator? In general, the advice to write your own userspace PRNG replacement for OpenSSL is not a good advice, because many people are not competent enough to do it. If you read my above post I clearly do not suggest this.
      - dchest 10y ago
        > I certainly wouldn't go anywhere near another NIST DRBG.. OK, this is an instant red-flag to me to get out of the conversation.
        forgotpwtomain 10y ago
        > OK, this is an instant red-flag to me to get out of the conversation. Perhaps you are unfamiliar with? https://en.wikipedia.org/wiki/Dual_EC_DRBG https://en.wikipedia.org/wiki/Dual_EC_DRBG
        dchest 10y ago
        I'm familiar with it. CTR DRBG, Hash DRBG, HMAC DRBG are all fairly solid designs.
tptacek 10y ago
ISAAC is a DRBG. It's like 1/3rd of a complete CSPRNG, and it's the easiest third to build. To use ISAAC securely on Linux, if for some reason you actually wanted to do that, you'd swap out the hash DRBG inside the kernel LRNG with ISAAC, and then continue using /dev/urandom. Simply replacing the OpenSSL RNG or /dev/urandom in userland code with the ISAAC routines is likely to blow your app up.

ISAAC (http://burtleburtle.net/bob/rand/isaacafa.html http://burtleburtle.net/bob/rand/isaacafa.html) for a CSPRNG. But what is your use-case for something non-standard? Just use /dev/urandom

derefr 10y ago

How about, backing the equivalent of /dev/urandom for a unikernel OS?

dchest 10y ago

No, no, no, don't use ISAAC.

forgotpwtomain 10y ago
Do you have a citation you can provide? I don't know of any research that has shown a significant weakness in ISAAC.
- dchest 10y ago
  Why would you use a PRNG with unknown cryptographic properties, not designed by a cryptographer, as opposed to one of the NIST's DRBG or a good stream cipher, such as ChaCha? Weakness: https://eprint.iacr.org/2006/438 https://eprint.iacr.org/2006/438 — "huge subsets of internal states which induce a strongly non-uniform distribution in the 8192 first bits produced" Finally, why is deterministic PRNG suggested as a replacement for OpenSSL's random number generator? In general, the advice to write your own userspace PRNG replacement for OpenSSL is not a good advice, because many people are not competent enough to do it.
  - forgotpwtomain 10y ago
    > as opposed to one of the NIST's DRBG I certainly wouldn't go anywhere near another NIST DRBG.. > https://eprint.iacr.org/2006/438 https://eprint.iacr.org/2006/438 From my brief understanding Aumasson's paper uses a different seeding routine from the example provided in the c implementation which allows the weaker states to be produced - indeed it's mentioned on the author's website. > Finally, why is deterministic PRNG suggested as a replacement for OpenSSL's random number generator? In general, the advice to write your own userspace PRNG replacement for OpenSSL is not a good advice, because many people are not competent enough to do it. If you read my above post I clearly do not suggest this.
    - dchest 10y ago
      > I certainly wouldn't go anywhere near another NIST DRBG.. OK, this is an instant red-flag to me to get out of the conversation.
      - forgotpwtomain 10y ago
        > OK, this is an instant red-flag to me to get out of the conversation. Perhaps you are unfamiliar with? https://en.wikipedia.org/wiki/Dual_EC_DRBG https://en.wikipedia.org/wiki/Dual_EC_DRBG
        dchest 10y ago
        I'm familiar with it. CTR DRBG, Hash DRBG, HMAC DRBG are all fairly solid designs.

tptacek 10y ago

ISAAC is a DRBG. It's like 1/3rd of a complete CSPRNG, and it's the easiest third to build. To use ISAAC securely on Linux, if for some reason you actually wanted to do that, you'd swap out the hash DRBG inside the kernel LRNG with ISAAC, and then continue using /dev/urandom. Simply replacing the OpenSSL RNG or /dev/urandom in userland code with the ISAAC routines is likely to blow your app up.