CASK derived keys. Fix HIS v1 derived keys.

michaelcfanning commented 4 months ago

BRK: Rename IdentifiableSecrets.ComputeDerivedSymmetricKey to ComputeDerivedIdentifiableKey.
BRK: Update IdentifiableSecrets.ComputeDerivedIdentifiableKey to accept an alternate checksum seed for constructing the derived key.
NEW: Add CommonAnnotatedSecret key class for next-generation identifiable secrets.
NEW: Add Identifiable.ComputeDerivedCommonAnnotatedKey to generate keys derived from common annotated secrets.

This change adds a new derived key API that is fully conformant with the next-generation common annotated security key standard, as well as a base class to instantiate and deconstruct individual elements of a CommonAnnotatedSecret.

This change additionally updates the older identifiable derived key computation to allow for the derived key checksum to diverge from the checksum of the parent key.

yongyan-gh commented 4 months ago

    derivedKeyBytes[31] = (byte)((derivedKeyBytes[31] & 0xC0) | 0b0111);

nit: can we have some comments what its doing here?

Refers to: src/Microsoft.Security.Utilities.Core/IdentifiableSecrets.cs:308 in fe5a8fd. [](commit_id = fe5a8fdfab06b3cfbd1eefad711bec23f829e9cd, deletion_comment = False)

michaelcfanning commented 4 months ago

    derivedKeyBytes[31] = (byte)((derivedKeyBytes[31] & 0xC0) | 0b0111);

Good idea, I will add this later. We are encoding deri in advance of the provider signature, an operation that's entirely non-obvious from this magic. :)

In reply to: 2123573592

Refers to: src/Microsoft.Security.Utilities.Core/IdentifiableSecrets.cs:308 in fe5a8fd. [](commit_id = fe5a8fdfab06b3cfbd1eefad711bec23f829e9cd, deletion_comment = False)

microsoft / security-utilities

CASK derived keys. Fix HIS v1 derived keys. #23