Return a json object form for the receiver.
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<KeyedCollection>
Returns the signature data as a ByteArray.
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<ByteArray>
Returns the combined protected and unprotected Jose header for this recipient.
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<SstJoseHeader>
Returns the protected header of this recipient
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<SstJoseHeader>
Returns the unprotected header of this recipient, which may be nil when there is none.
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<SstJoseHeader | UndefinedObject>