Class SM9KeyExchange

java.lang.Object

org.bouncycastle.crypto.agreement.SM9KeyExchange

public class SM9KeyExchange
extends Object

The SM9 key exchange protocol (GM/T 0044.3-2016).

Usage per party: construct with your own key-exchange private key (derived under the KGC's published hid), the peer's identity, and whether you are the initiator (user A) or responder (user B). Call generateEphemeral(SecureRandom) to produce your R value, exchange R values, then call calculateKey(int, ECPoint) with the peer's R to obtain the shared key. The optional key-confirmation tags are then available via getResponderConfirmation() (S_B) and getInitiatorConfirmation() (S_A).

Constructor Summary

Constructors

Constructor	Description
SM9KeyExchange(SM9EncPrivateKeyParameters key, byte[] peerIdentity, boolean initiator)

Method Summary

Modifier and Type	Method	Description
byte[]	calculateKey(int klenBits, ECPoint peerR)	Compute the shared key of klenBits bits from the peer's ephemeral value peerR.
ECPoint	generateEphemeral(SecureRandom random)	Generate this party's ephemeral value R = [r]Q_peer (a G1 point) and retain the ephemeral scalar r.
byte[]	getInitiatorConfirmation()	S_A = Hash(0x83 || g1 || Hash(g2||g3||IDA||IDB||RA||RB)): the confirmation the initiator sends to (and the responder checks against) the responder.
byte[]	getResponderConfirmation()	S_B = Hash(0x82 || g1 || Hash(g2||g3||IDA||IDB||RA||RB)): the confirmation the responder sends to (and the initiator checks against) the initiator.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

SM9KeyExchange

public SM9KeyExchange(SM9EncPrivateKeyParameters key,
 byte[] peerIdentity,
 boolean initiator)

Method Details

generateEphemeral

public ECPoint generateEphemeral(SecureRandom random)

Generate this party's ephemeral value R = [r]Q_peer (a G1 point) and retain the ephemeral scalar r. Q_peer = [H1(peerIdentity||hid, N)]P1 + P_pub-e, using the hid this party's own key was derived under - both parties' keys come from the same KGC, which publishes the hid it chose.

calculateKey

public byte[] calculateKey(int klenBits,
 ECPoint peerR)

Compute the shared key of klenBits bits from the peer's ephemeral value peerR. Must be called after generateEphemeral(SecureRandom).

getResponderConfirmation

public byte[] getResponderConfirmation()

S_B = Hash(0x82 || g1 || Hash(g2||g3||IDA||IDB||RA||RB)): the confirmation the responder sends to (and the initiator checks against) the initiator.

The returned tag is a secret authenticator; a received value must be compared against it with Arrays.constantTimeAreEqual(byte[], byte[]), not Arrays.equals, to avoid a timing side channel.

getInitiatorConfirmation

public byte[] getInitiatorConfirmation()

S_A = Hash(0x83 || g1 || Hash(g2||g3||IDA||IDB||RA||RB)): the confirmation the initiator sends to (and the responder checks against) the responder.

The returned tag is a secret authenticator; a received value must be compared against it with Arrays.constantTimeAreEqual(byte[], byte[]), not Arrays.equals, to avoid a timing side channel.