SHA256 is an instance of SHA2. Presumably you didn't mean that SHA512 was bad, or, better, SHA512/256.
Right. But I don't see a reason why you would ever want either of those when SHA256 works just fine. Maybe because it's a bit more efficient per byte as a PRNG, but there are better specialized tools for that.
ECDSA has another problem: it has a hard randomness requirement.
Not if you use RFC6979. In the Bitcoin space that's been standard since about three days after the Java.SecureRandom bug. As for curves, secp256k1 and curve25519 seem to be the most popular as far as I can tell.
One-time pads are awful and should be avoided at all costs. Virtually every computer program developed by generalist programmers that claimed to be a "one-time pad" was instead a crappy stream cipher.
Well, yes, an OTP generated by a PRNG is a stream cipher by definition. You do need true randomness for them to work. I think they're very useful if (1) you're scared that NSA has a constructive proof of P=NP deep inside their lairs, or (2) you want ultimate deniable encryption.
Comments
Right. But I don't see a reason why you would ever want either of those when SHA256 works just fine. Maybe because it's a bit more efficient per byte as a PRNG, but there are better specialized tools for that.
Not if you use RFC6979. In the Bitcoin space that's been standard since about three days after the Java.SecureRandom bug. As for curves, secp256k1 and curve25519 seem to be the most popular as far as I can tell.
Well, yes, an OTP generated by a PRNG is a stream cipher by definition. You do need true randomness for them to work. I think they're very useful if (1) you're scared that NSA has a constructive proof of P=NP deep inside their lairs, or (2) you want ultimate deniable encryption.
SHA512/256 is safer than SHA256, for more than one reason. secp256k1 is "popular" for cryptocoins.