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diff --git a/docs/feedback.md b/docs/feedback.md new file mode 100644 index 0000000..d79d57f --- /dev/null +++ b/docs/feedback.md @@ -0,0 +1,23 @@ +# Feedback + +This document describes the integrity-protected file format that a trusted +system uses when making legitimately issued certificates available to a monitor. + +## Format + + NAME MAC + <CERTIFICATE CHAIN> + ... + <CERTIFICATE CHAIN> + +`NAME`: identifier that the monitor uses to locate the shared secret. + +`MAC`: HMAC with SHA256 as the hash function, computed for line two and forward. +The shared HMAC key is derived as follows by the trusted system and the monitor: + + hkdf := hkdf.New(sha256.New, SECRET, []byte("silentct"), NAME) + key := make([]byte, 16) + io.ReadFull(hkdf, key) + +`<CERTIFICATE CHAIN>`: certificate chain in PEM format that the trusted system +considers legitimate. Can be repeated, then delimited by "silentct:separator". |