C_hash Code hash value.

C_hash value is the base64url encoding of the left-most half of the hash of the octets of the ASCII representation of the code value, where the hash algorithm used is the hash algorithm used in the alg Header Parameter of the id_token's JOSE Header. For instance, if the alg is HS512, hash the code value with SHA-512, then take the left-most 256 bits and base64url encode them.

The C_hash value is a case-sensitive string.

If the id_token is issued from the Authorization_endpoint with a code, which is the case for the response_type values code id_token and code id_token token, this is REQUIRED; otherwise, its inclusion is OPTIONAL.

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