Lets say I have a seed named iv which has a decent amount of entropy.
Are there any glaring issues with the following?
First 64 bytes are generated by SHA512(iv)
Next 64 bytes are generated by HMAC_SHA512(iv, Previous64Bytes)
and so on...
Obviously if I needed "perfect" security I could use something like HMAC-DRBG (NIST SP 800-90), but I need something that's good enough, easy to implement and I do not care if a supercomputer breaks it in 10 years.
Edit - More info:
- This will not be used to generate more than 500 bytes of data per run
- Speed of the algorithm doesn't matter