The three steps from Section 4.3 on Registration are essentially the same. To verify the signature you have to retrieve the issuer credentials and you have to do item 4.
Issuer Verification: The Transparency Service MUST
syntactically validate the Issuer's identity Claims, which may be
different than the Client identity.
Signature verification: The Transparency Service MUST verify
the signature of the Signed Statement, as described in [RFC9360],
using the signature algorithm and verification key of the Issuer.
Signed Statement validation: The Transparency Service MUST
check that the Signed Statement includes the required protected
headers listed above. The Transparency Service MAY verify the
Statement payload format, content and other optional properties.
The three steps from Section 4.3 on Registration are essentially the same. To verify the signature you have to retrieve the issuer credentials and you have to do item 4.
Issuer Verification: The Transparency Service MUST syntactically validate the Issuer's identity Claims, which may be different than the Client identity.
Signature verification: The Transparency Service MUST verify the signature of the Signed Statement, as described in [RFC9360], using the signature algorithm and verification key of the Issuer.
Signed Statement validation: The Transparency Service MUST check that the Signed Statement includes the required protected headers listed above. The Transparency Service MAY verify the Statement payload format, content and other optional properties.