Misleading name for IsDERSignature function #5284

This function takes in not a DER signature, but a DER signature appended with hashtype byte.

I suggest calling plain DER signature a "signature" and a signature with hashtype - "script signature".

So the functions could be renamed like so:

IsDERSignature -> IsValidScriptSignature IsLowDERSignature -> IsLowScriptSignature IsDefinedHashtypeSignature -> IsValidHashtypeInScriptSignature

In fact, I don't see a good reason to allow invalid hashtypes at all. Validity of hashtype should probably go right in general verification code (in IsDERSignature).

Thoughts?

I understand the confusion. The name of the function means "is this a (script) signature with valid DER?".

Also, there is no such thing as an invalid hashtype. All 256 values for the hashtype byte are valid. There are just only 6 intended ones.

The reason for splitting DER off from hashtype checks is because DER violations pose a malleability problem (which BIP62 plans to make illegal in a softfork), while the unknown hashtypes are at most a minor implementation complication, and only made nonstandard for now.

As we do not longer have such function (it was renamed to IsValidSignatureEncoding thus solving this issue), can we close this?