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HappyEmu / ace

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OSCORE key derivation #1

Closed DurandA closed 6 years ago

DurandA commented 6 years ago

When reading draft-ietf-core-object-security-08, I noticed they settled on HKDF (RFC5869) — with HKDF SHA-256 being mandatory) for key derivation.

Should HKDF replace EDHOC? I also noticed that both draft-ietf-core-object-security-08 and draft-selander-ace-cose-ecdhe-07 are from the same authors.

HappyEmu commented 6 years ago

Not sure if I understand the question correctly.

HKDF is only used to derive keys from a previously established master secret. How this master secret is established is being left to the application to implement and it's exactly what EDHOC does:

image

After EDHOC, we end up with all the required parameters (master secret, master salt, recipient and sender IDs, HKDF, AEAD, etc...)

HappyEmu commented 6 years ago

The workflow implemented right now is the one described in Appendix B (and B.1) of https://www.ietf.org/id/draft-ietf-ace-oscore-profile-00.txt where we use the PoP key bound to the access token to authenticate the messages in EDHOC.

DurandA commented 6 years ago

Thanks for the clarification.