3.1.2 ASN.1 Syntax for DER-encoding Public Key used for Encryption

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The Diffie-Hellman public key used for ElGamal encryption MUST be DER-encoded as follows (using ASN.1 syntax):

 DHPublicKeyForElGamalEncryption::= SEQUENCE {
       p    INTEGER, -- prime, p
       q    INTEGER OPTIONAL, -- factor of p-1, only present when p = j*q+1,
                              -- where j is not 2
       g    INTEGER, -- generator, g
       y    INTEGER -- public key (g^x mod p, where x is the private key)
 }

Diffie-Hellman is a cryptographic key exchange protocol that allows two parties that have no prior knowledge of each other to jointly establish a shared secret over an insecure communications channel, as specified in [CRYPTO].

Rivest, Shamir and Adleman (RSA) is a cryptographic protocol as specified in [CRYPTO].

The RSA public key used for RSA encryption MUST be DER-encoded as follows (using ASN.1 syntax):

 RSAPublicKeyForRSAEncryption::= SEQUENCE {
       modulus           INTEGER, -- the RSA modulus n
       publicExponent    INTEGER  -- the RSA public exponent e
 }