static bool locallyVerifyUserStatement(S signed) {
  try {
    L<S> lines = toLines(signed);
    S authorLine = lines.get(lines.size()-2);
    S sigLine = lines.get(lines.size()-1);
    S text = fromLines(lines.subList(0, lines.size()-1));
    S author = dropPrefixMandatory("-", authorLine);
    S cid = trim(dropSuffix("[user]", author));
    if (!isComputerID(cid)) fail("Not a computer ID: " + cid);
    byte[] publicKey = PKI.userPublicKey();
    S sig = dropPrefixMandatory("sig: ", sigLine);
    ret PKI.verifySignature(publicKey, PKI.signatureFromString(sig), toUtf8(text));
  } catch (RuntimeException e) {
    ret false;
  }
}

Began life as a copy of #1001567