RSA-OAEP vs. RSA-OAEP-MGF1P

[Cantor, Scott]

> In practice, though, what the IdP is interpreting it as meaning appears to be
> only MGF1 with SHA-1, which after all is what it means when you use it in the
> encryption context. So it's redundant as things stand.

I think the IdP just defaults to SHA-1 now because of interop, so I'm not sure it's explicitly interpreting anything, you wouldn't be able to tell really. In other words, I don't think it's looking for opportunities to use SHA-2, but I could be wrong.

Spec-wise, the language isn't as clear as it could be, but this line:

"In the absence of an element describing support for a particular algorithm type (e.g., no <alg:DigestMethod> elements), the metadata consumer is free to select any algorithm that it supports. The absence of metadata therefore implies no information, rather than lack of support."

was meant to apply not only to top-level elements, but also parameters of algorithms.

> I think I'd want a spec somewhere to say something specific about this
> before proposing that we change the IdP to assume it means the SP can
> handle other digest functions than SHA-1.

The spec doesn't not say that, if that makes sense.

-- Scott