Any RNG can be used for ECC keys. sha256("fijewfeifjewijfiewjfiewiwegj9") = 70c99bd41eac18009667fba5b1bfaeff720c08eb3dfac081f0fe3758a87af1b8 I just generated an ECDH-256 private key with sha256 and random typing on the keyboard. The trickier part is making the public key from the private key. I can do that too, but would need to write a little C program and use OpenSSL.