I'm using OpenSSL 1.0.2 and FOM 2.16 and am trying to figure out a way to draw entropy from Intel (RDRAND/RDSEED) if it's available, and from the Linux OS (/dev/random or /dev/urandom) if it's not. If I build OpenSSL with --with-rand-seed=rdcpu,os it tries to get entropy first from the Linux OS. I need it to try RDRAND/RDSEED first (for certification reasons), but fall back on the Linux OS if RDRAND/RDSEED isn't available. Does anyone know a way to do this?

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  • $\begingroup$ The configuration you have may not be what you want, but it is secure and reasonable. You're going to be better off looking at the source code to see if what you want is possible, and/or trying with a newer version (since OpenSSL 1.0.2 is no longer supported publicly). $\endgroup$
    – bk2204
    Aug 5 at 22:03
  • $\begingroup$ 1.0.2 came with a RDRAND engine. You should be able to use that, see github.com/openssl/openssl/blob/OpenSSL_1_0_2-stable/crypto/… $\endgroup$ Aug 6 at 3:22


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