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package org.bouncycastle.crypto.hpke;
import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.Pack;
import org.bouncycastle.util.Strings;
public class HPKE
{
// modes
public static final byte mode_base = 0x00;
public static final byte mode_psk = 0x01;
public static final byte mode_auth = 0x02;
public static final byte mode_auth_psk = 0x03;
// kems
public static final short kem_P256_SHA256 = 16;
public static final short kem_P384_SHA348 = 17;
public static final short kem_P521_SHA512 = 18;
public static final short kem_X25519_SHA256 = 32;
public static final short kem_X448_SHA512 = 33;
// kdfs
public static final short kdf_HKDF_SHA256 = 0x0001;
public static final short kdf_HKDF_SHA384 = 0x0002;
public static final short kdf_HKDF_SHA512 = 0x0003;
// aeads
public static final short aead_AES_GCM128 = 0x0001;
public static final short aead_AES_GCM256 = 0x0002;
public static final short aead_CHACHA20_POLY1305 = 0x0003;
public static final short aead_EXPORT_ONLY = (short) 0xFFFF;
private final byte[] default_psk = null;
private final byte[] default_psk_id = null;
private final byte mode;
private final short kemId;
private final short kdfId;
private final short aeadId;
private final DHKEM dhkem;
private final HKDF hkdf;
short Nk;
/**
* Hybrid Public Key Encryption as described in RFC9180.
*
* @see
* RFC9180 An implementation of the Hybrid Public Key Encryption.
*/
public HPKE(byte mode, short kemId, short kdfId, short aeadId)
{
this.mode = mode;
this.kemId = kemId;
this.kdfId = kdfId;
this.aeadId = aeadId;
this.hkdf = new HKDF(kdfId);
this.dhkem = new DHKEM(kemId);
if (aeadId == aead_AES_GCM128)
{
Nk = 16;
}
else
{
Nk = 32;
}
}
public int getEncSize()
{
switch (kemId)
{
case HPKE.kem_P256_SHA256:
return 65;
case HPKE.kem_P384_SHA348:
return 97;
case HPKE.kem_P521_SHA512:
return 133;
case HPKE.kem_X25519_SHA256:
return 32;
case HPKE.kem_X448_SHA512:
return 56;
default:
throw new IllegalArgumentException("invalid kem id");
}
}
public short getAeadId()
{
return aeadId;
}
private void VerifyPSKInputs(byte mode, byte[] psk, byte[] pskid)
{
boolean got_psk = (!Arrays.areEqual(psk, default_psk));
boolean got_psk_id = (!Arrays.areEqual(pskid, default_psk_id));
if (got_psk != got_psk_id)
{
throw new IllegalArgumentException("Inconsistent PSK inputs");
}
if (got_psk && (mode % 2 == 0))
{
throw new IllegalArgumentException("PSK input provided when not needed");
}
if ((!got_psk) && (mode % 2 == 1))
{
throw new IllegalArgumentException("Missing required PSK input");
}
}
private HPKEContext keySchedule(byte mode, byte[] sharedSecret, byte[] info, byte[] psk, byte[] pskid)
{
VerifyPSKInputs(mode, psk, pskid);
byte[] suiteId = Arrays.concatenate(
Strings.toByteArray("HPKE"),
Pack.shortToBigEndian(kemId),
Pack.shortToBigEndian(kdfId),
Pack.shortToBigEndian(aeadId));
byte[] pskidHash = hkdf.LabeledExtract(null, suiteId, "psk_id_hash", pskid);
byte[] infoHash = hkdf.LabeledExtract(null, suiteId, "info_hash", info);
byte[] modeArray = new byte[1];
modeArray[0] = mode;
byte[] keyScheduleContext = Arrays.concatenate(modeArray, pskidHash, infoHash);
byte[] secret = hkdf.LabeledExtract(sharedSecret, suiteId, "secret", psk);
byte[] key = hkdf.LabeledExpand(secret, suiteId, "key", keyScheduleContext, Nk);
byte[] base_nonce = hkdf.LabeledExpand(secret, suiteId, "base_nonce", keyScheduleContext, 12);//Nn
byte[] exporter_secret = hkdf.LabeledExpand(secret, suiteId, "exp", keyScheduleContext, hkdf.getHashSize());//todo Nk*2 with replace hash digest size
return new HPKEContext(new AEAD(aeadId, key, base_nonce), hkdf, exporter_secret, suiteId);
}
public AsymmetricCipherKeyPair generatePrivateKey()
{
return dhkem.GeneratePrivateKey();
}
public byte[] serializePublicKey(AsymmetricKeyParameter pk)
{
return dhkem.SerializePublicKey(pk);
}
public byte[] serializePrivateKey(AsymmetricKeyParameter sk)
{
return dhkem.SerializePrivateKey(sk);
}
public AsymmetricKeyParameter deserializePublicKey(byte[] pkEncoded)
{
return dhkem.DeserializePublicKey(pkEncoded);
}
public AsymmetricCipherKeyPair deserializePrivateKey(byte[] skEncoded, byte[] pkEncoded)
{
return dhkem.DeserializePrivateKey(skEncoded, pkEncoded);
}
public AsymmetricCipherKeyPair deriveKeyPair(byte[] ikm)
{
return dhkem.DeriveKeyPair(ikm);
}
public byte[][] sendExport(AsymmetricKeyParameter pkR, byte[] info, byte[] exporterContext, int L,
byte[] psk, byte[] pskId, AsymmetricCipherKeyPair skS)
{
HPKEContextWithEncapsulation ctx;
byte[][] output = new byte[2][]; // ct and enc
switch (mode)
{
case mode_base:
ctx = setupBaseS(pkR, info);
break;
case mode_auth:
ctx = setupAuthS(pkR, info, skS);
break;
case mode_psk:
ctx = SetupPSKS(pkR, info, psk, pskId);
break;
case mode_auth_psk:
ctx = setupAuthPSKS(pkR, info, psk, pskId, skS);
break;
default:
throw new IllegalStateException("Unknown mode");
}
output[0] = ctx.encapsulation;
output[1] = ctx.export(exporterContext, L);
return output;
}
public byte[] receiveExport(byte[] enc, AsymmetricCipherKeyPair skR, byte[] info, byte[] exporterContext, int L,
byte[] psk, byte[] pskId, AsymmetricKeyParameter pkS)
{
HPKEContext ctx;
switch (mode)
{
case mode_base:
ctx = setupBaseR(enc, skR, info);
break;
case mode_auth:
ctx = setupAuthR(enc, skR, info, pkS);
break;
case mode_psk:
ctx = setupPSKR(enc, skR, info, psk, pskId);
break;
case mode_auth_psk:
ctx = setupAuthPSKR(enc, skR, info, psk, pskId, pkS);
break;
default:
throw new IllegalStateException("Unknown mode");
}
return ctx.export(exporterContext, L);
}
public byte[][] seal(AsymmetricKeyParameter pkR, byte[] info, byte[] aad, byte[] pt,
byte[] psk, byte[] pskId, AsymmetricCipherKeyPair skS)
throws InvalidCipherTextException
{
HPKEContextWithEncapsulation ctx;
byte[][] output = new byte[2][]; // ct and enc
switch (mode)
{
case mode_base:
ctx = setupBaseS(pkR, info);
break;
case mode_auth:
ctx = setupAuthS(pkR, info, skS);
break;
case mode_psk:
ctx = SetupPSKS(pkR, info, psk, pskId);
break;
case mode_auth_psk:
ctx = setupAuthPSKS(pkR, info, psk, pskId, skS);
break;
default:
throw new IllegalStateException("Unknown mode");
}
output[0] = ctx.seal(aad, pt);
output[1] = ctx.getEncapsulation();
return output;
}
public byte[] open(byte[] enc, AsymmetricCipherKeyPair skR, byte[] info, byte[] aad, byte[] ct,
byte[] psk, byte[] pskId, AsymmetricKeyParameter pkS)
throws InvalidCipherTextException
{
HPKEContext ctx;
switch (mode)
{
case mode_base:
ctx = setupBaseR(enc, skR, info);
break;
case mode_auth:
ctx = setupAuthR(enc, skR, info, pkS);
break;
case mode_psk:
ctx = setupPSKR(enc, skR, info, psk, pskId);
break;
case mode_auth_psk:
ctx = setupAuthPSKR(enc, skR, info, psk, pskId, pkS);
break;
default:
throw new IllegalStateException("Unknown mode");
}
return ctx.open(aad, ct);
}
public HPKEContextWithEncapsulation setupBaseS(AsymmetricKeyParameter pkR, byte[] info)
{
byte[][] output = dhkem.Encap(pkR); // sharedSecret, enc
HPKEContext ctx = keySchedule(mode_base, output[0], info, default_psk, default_psk_id);
return new HPKEContextWithEncapsulation(ctx, output[1]);
}
// Variant of setupBaseS() where caller can provide their own ephemeral key pair.
// This should only be used to validate test vectors.
public HPKEContextWithEncapsulation setupBaseS(AsymmetricKeyParameter pkR, byte[] info, AsymmetricCipherKeyPair kpE)
{
byte[][] output = dhkem.Encap(pkR, kpE); // sharedSecret, enc
HPKEContext ctx = keySchedule(mode_base, output[0], info, default_psk, default_psk_id);
return new HPKEContextWithEncapsulation(ctx, output[1]);
}
public HPKEContext setupBaseR(byte[] enc, AsymmetricCipherKeyPair skR, byte[] info)
{
byte[] sharedSecret = dhkem.Decap(enc, skR);
return keySchedule(mode_base, sharedSecret, info, default_psk, default_psk_id);
}
public HPKEContextWithEncapsulation SetupPSKS(AsymmetricKeyParameter pkR, byte[] info, byte[] psk, byte[] psk_id)
{
byte[][] output = dhkem.Encap(pkR); // sharedSecret, enc
HPKEContext ctx = keySchedule(mode_psk, output[0], info, psk, psk_id);
return new HPKEContextWithEncapsulation(ctx, output[1]);
}
public HPKEContext setupPSKR(byte[] enc, AsymmetricCipherKeyPair skR, byte[] info, byte[] psk, byte[] psk_id)
{
byte[] sharedSecret = dhkem.Decap(enc, skR);
return keySchedule(mode_psk, sharedSecret, info, psk, psk_id);
}
public HPKEContextWithEncapsulation setupAuthS(AsymmetricKeyParameter pkR, byte[] info, AsymmetricCipherKeyPair skS)
{
byte[][] output = dhkem.AuthEncap(pkR, skS);
HPKEContext ctx = keySchedule(mode_auth, output[0], info, default_psk, default_psk_id);
return new HPKEContextWithEncapsulation(ctx, output[1]);
}
public HPKEContext setupAuthR(byte[] enc, AsymmetricCipherKeyPair skR, byte[] info, AsymmetricKeyParameter pkS)
{
byte[] sharedSecret = dhkem.AuthDecap(enc, skR, pkS);
return keySchedule(mode_auth, sharedSecret, info, default_psk, default_psk_id);
}
public HPKEContextWithEncapsulation setupAuthPSKS(AsymmetricKeyParameter pkR, byte[] info, byte[] psk, byte[] psk_id, AsymmetricCipherKeyPair skS)
{
byte[][] output = dhkem.AuthEncap(pkR, skS);
HPKEContext ctx = keySchedule(mode_auth_psk, output[0], info, psk, psk_id);
return new HPKEContextWithEncapsulation(ctx, output[1]);
}
public HPKEContext setupAuthPSKR(byte[] enc, AsymmetricCipherKeyPair skR, byte[] info, byte[] psk, byte[] psk_id, AsymmetricKeyParameter pkS)
{
byte[] sharedSecret = dhkem.AuthDecap(enc, skR, pkS);
return keySchedule(mode_auth_psk, sharedSecret, info, psk, psk_id);
}
}