[tor-commits] [torspec/master] Explain algorithm field on directory-signature

[nickm at torproject.org]

commit 96427e8daa30e68d1b3cba13220fea84a4e8e842
Author: Nick Mathewson <nickm at torproject.org>
Date:   Fri Nov 23 10:51:18 2012 -0500

    Explain algorithm field on directory-signature
    
    Fix for 7072
---
 dir-spec.txt |   20 +++++++++++++++++++-
 1 files changed, 19 insertions(+), 1 deletions(-)

diff --git a/dir-spec.txt b/dir-spec.txt
index 8e389c9..ca5434b 100644
--- a/dir-spec.txt
+++ b/dir-spec.txt
@@ -1532,7 +1532,8 @@
    The signature contains the following item, which appears Exactly Once
    for a vote, and At Least Once for a consensus.
 
-    "directory-signature" SP identity SP signing-key-digest NL Signature
+    "directory-signature" [SP Algorithm] SP identity SP signing-key-digest
+        NL Signature
 
         This is a signature of the status document, with the initial item
         "network-status-version", and the signature item
@@ -1543,6 +1544,20 @@
         the signing authority, and "signing-key-digest" is the hex-encoded
         digest of the current authority signing key of the signing authority.
 
+        The Algorithm is one of "sha1" or "sha256" if it is present;
+        implementations MUST ignore directory-signature entries with an
+        unrecognized Algorithm.  "sha1" is the default, if no Algorithm is
+        given.  The algorithm describes how to compute the hash of the
+        document before signing it.
+
+        "ns"-flavored consensus documents must contain only sha1 signatures.
+        Votes and microdescriptor documents may contain other signature
+        types. Note that only one signature from each authority should be
+        "counted" as meaning that the authority has signed the consensus.
+
+        (Tor clients before 0.2.3.x did not understand the 'algorithm'
+        field.)
+
 3.4. Assigning flags in a vote
 
    (This section describes how directory authorities choose which status
@@ -2101,6 +2116,9 @@
         [*Before consensus method 13, this field was sometimes erroneously
         omitted.]
 
+   Additionally, a microdescriptor consensus MAY use the sha256 digest
+   algorithm for its signatures.
+
 3.7. Detached signatures
 
    Assuming full connectivity, every authority should compute and sign the