S_hash is the OAuth state parameter hash value and is the base64url encoding of the left-most half of the hash of the octets of the ASCII representation of the state value, where the hash algorithm used is id_token's alg JOSE Header Parameter Header.

S_hash value is a Case-sensitive string.

For example, if the alg is HS512, hash the code value with SHA-512, then take the left-most 256 bits and base64url encode them.

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