Module: Secp256k1::ECDH

Included in:
Secp256k1
Defined in:
lib/secp256k1/ecdh.rb

Overview

ECDH module.

Examples:

include Secp256k1

alice_sk, alice_pk = generate_key_pair
bob_sk, bob_pk = generate_key_pair

# Both parties compute the same shared secret.
ecdh(bob_pk, alice_sk) == ecdh(alice_pk, bob_sk)

Instance Method Summary collapse

Instance Method Details

#ecdh(pubkey, private_key, hash_function: nil) ⇒ String

Compute an EC Diffie-Hellman shared secret.

Parameters:

  • pubkey (String) —

    the other party’s public key with hex format.

  • private_key (String) —

    your private key with hex format.

  • hash_function (FFI::Pointer) (defaults to: nil) —

    (Optional)A pointer to the hash function to use. If omitted, the library default(SHA256 of the compressed point) is used. See C.ecdh_hash_function_sha256.

Returns:

  • (String) —

    32-byte shared secret with hex format.

Raises:

  • (Secp256k1::Error) —

    If the secret was invalid or the public key could not be parsed.

  • (ArgumentError) —

    If invalid arguments specified.



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# File 'lib/secp256k1/ecdh.rb', line 22

def ecdh(pubkey, private_key, hash_function: nil)
  raise ArgumentError, "pubkey must be String." unless pubkey.is_a?(String)
  validate_string!("private_key", private_key, 32)
  pubkey = hex2bin(pubkey)
  private_key = hex2bin(private_key)
  with_context do |context|
    internal = parse_pubkey_internal(context, pubkey)
    seckey = FFI::MemoryPointer.new(:uchar, 32).put_bytes(0, private_key)
    output = FFI::MemoryPointer.new(:uchar, 32)
    hashfp = hash_function || FFI::Pointer::NULL
    raise Error, 'secp256k1_ecdh failed.' unless secp256k1_ecdh(context, output, internal, seckey, hashfp, nil) == 1
    output.read_string(32).unpack1('H*')
  end
end