openpgp: Change general purpose keys to have a signing subkey.

  - Certificates with a primary key that is not signing capable, and a
    subkey that is, are strictly more secure than ones that combine
    signing and certification capabilities in the primary key.

  - If the owner of a certificate with a signing-capable primary key
    can be tricked into creating a binary signature over carefully
    chosen attacker-controlled data, this signature can be repurposed
    to bind arbitrary attacker-controlled components to the
    certificate using a chosen-prefix collision attack on the hash
    function (see e.g.  "SHA-1 is a Shambles" for a similar attack).

  - Having a separate signing-subkey mitigates the attack, because
    signatures by the signing subkey cannot bind components to the
    certificate.

0 files changed, 0 insertions, 0 deletions