Signature specification without certificates



Signatures are inambiguously specified when embedded in an X.509
certificate, as per the following ASN.1 defined in RFC 3280:

Certificate ::= SEQUENCE {
tbsCertificate TBSCertificate,
signatureAlgorithm AlgorithmIdentifier,
signatureValue BIT STRING
}

How does one specify signatures without using certificates? I guess one
could use a type like

SignatureInfo ::= SEQUENCE {
signatureAlgorithm AlgorithmIdentifier,
signatureValue BIT STRING
}

However, I have yet to find an RFC or some other standard in which such a
thing is discussed. Can anybody help?

.