Relying Party - Any entity that uses a digital certificate to identify the creator of digitally signed information, verify the integrity of digitally signed information, or establish confidential communication with the holder of a certificate by relying on the validity of the binding the subscriber's name to the public key contained in the certificate. E2.1.22.
NIST IR 7298
NIST SP 800-102
NIST SP 800-103 Draft
NIST SP 800-116
Relying Party - In this publication, an entity, such as a PACS, that depends upon the trust model of the PIV System to correctly produce the results of authentication, i.e., the identity of the cardholder.
NIST SP 800-32
Relying Party - A person or Agency who has received information that includes a certificate and a digital signature verifiable with reference to a public key listed in the certificate, and is in a position to rely on them.
NIST SP 800-57P2
Relying Party - An entity that relies on received information for authentication purposes.