SignatureSubpacketTag
CreationTime = 2
EmbeddedSignature = 32
ExpireTime = 3
Exportable = 4
Features = 30
IssuerKeyId = 16
KeyExpireTime = 9
KeyFlags = 27
KeyServerPreferences = 23
NotationData = 20
Placeholder = 10
PolicyUrl = 26
PreferredKeyServer = 24
PrimaryUserId = 25
RegExp = 6
Revocable = 7
RevocationKey = 12
RevocationReason = 29
SignatureTarget = 31
SignerUserId = 28
TrustSig = 5