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Document RSA->Ed crosscert format

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Nick Mathewson 2017-09-20 13:43:32 -04:00
parent 6b14f76ec1
commit bfdc69a1e9
1 changed files with 24 additions and 3 deletions
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cert-spec.txt
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@ -24,7 +24,7 @@
2. Document formats
2.1. Certificates
2.1. Ed25519 Certificates
When generating a signing key, we also generate a certificate for it.
Unlike the certificates for authorities' signing keys, these
@ -90,6 +90,27 @@
When this extension is present, it MUST match the key used to
sign the certificate.
2.3. RSA->Ed25519 cross-certificate
Certificate type [07] (Cross-certification of Ed25519 identity
with RSA key) contains the following data:
ED25519_KEY [32 bytes]
EXPIRATION_DATE [4 bytes]
SIGLEN [1 byte]
SIGNATURE [SIGLEN bytes]
Here, the Ed25519 identity key is signed with router's RSA
identity key, to indicate that authenticating with a key
certified by the Ed25519 key counts as certifying with RSA
identity key. (The signature is computed on the SHA256 hash of
the non-signature parts of the certificate, prefixed with the
string "Tor TLS RSA/Ed25519 cross-certificate".)
This certificate type is used to mean, "This Ed25519 identity key
acts with the authority of the RSA key that signed this
certificate."
A.1. List of certificate types
The values marked with asterisks are not types corresponding to
@ -111,8 +132,8 @@ A.1. List of certificate types
[06] - Ed25519 authentication key signed with ed25519 signing key
(see prop220 section 4.2)
[07] - RSA identity cross-certification
(see prop220 section 4.2)
**[07] - Reserved for RSA identity cross-certification;
(see section 2.3 above, and tor-spec.txt section 4.2)
[08] - Onion service: short-term descriptor signing key, signed
with blinded public key.