New answers tagged csprng
Yes, you are reading this right. The requests for random value from NIST 800-90 drbgs perturbed the state. If this is a problem you can add a layer that optionally buffers values and always makes constant size requests.
If you start with a random key and zero counter, there's 128 bits of entropy in the system state. If you start with a random key and random counter value, there's 256 bits of entropy. Whether that matters depends on what you are using the PRNG output for. If you are using the output for anything where 256 bits of entropy would be an asset – say random ...
When using counter mode you can start at any value, it doesn't matter. The only important thing is that you never use the same counter value twice for the lifetime of the key. So, as long as your key is actually random and, as you say, you don't use it for more than 1 MB of data, then your generator should be fine.
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