account-key assertion

The account-key assertion holds a public key belonging to an account.

The format is as follows:

type:                account-key
authority-id:        <authority account id>
revision:            <int>
public-key-sha3-384: <key id/sha3-384 digest of the key>
account-id:          <account id>
name:                <human readable key name>
since:               <UTC datetime>
until:               <UTC datetime>
sign-key-sha3-384:   <key id> # Encoded key id of signing key

BODY: base64 encoded version prefixed public key packet

<signature>                 # Encoded signature

The index for this assertion is public-key-sha3-384. The key is valid in the time interval specified by since and until, being valid forever if until, which is optional, is not defined.

public-key-sha3-384 is the SHA3-384 hash of the (decoded) body content. The body itself is a format version byte (0x1 for now) followed by the public key packet itself. The version 1 public key packet is a constrained/normalized RFC4880 public key packet (v4, new header format, algorithm fixed to RSA, timestamp fixed as well).

The digest of the public key (public-key-sha3-384) is used for the lookup of keys when verifying signatures: all assertions reference their signing key by providing this digest in a sign-key-sha3-384 header.

Note that when validating an account-key it is essential to check that the digest matches the assertion body, besides the signature validation performed for all assertions.

This kind of assertion is used to transmit key information beween the store and snapd so the later can validate assertions signed by the key owner. It is one of the assertions that you get when downloading a package with sudo download <snap name>.

As an example, Canonical's public key for the store is

type: account-key
authority-id: canonical
revision: 2
public-key-sha3-384: BWDEoaqyr25nF5SNCvEv2v7QnM9QsfCc0PBMYD_i2NGSQ32EF2d4D0hqUel3m8ul
account-id: canonical
name: store
since: 2016-04-01T00:00:00.0Z
body-length: 717
sign-key-sha3-384: -CvQKAwRQ5h3Ffn10FILJoEZUXOv6km9FwA80-Rcj-f-6jadQ89VRswHNiEB9Lxk

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