This specification defines a means of computing a thumbprint value (a.k.a. digest) of JSON Web Key (JWK) objects analogous to the "x5t" (X.509 Certificate SHA-1 Thumbprint) value defined for X.509 certificate objects. This specification also registers the new JSON Web Signature (JWS) and JSON Web Encryption (JWE) Header Parameters and the new JSON Web Key (JWK) member name "jkt" (JWK SHA-256 Thumbprint) for holding these values.