* ASN.1 syntax for EC private keys from SEC 1 v1.5 (draft): * *
* EXPLICIT TAGS
*
* ECPrivateKey ::= SEQUENCE {
* version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
* privateKey OCTET STRING,
* parameters [0] ECDomainParameters {{ SECGCurveNames }} OPTIONAL,
* publicKey [1] BIT STRING OPTIONAL
* }
*
*
* We currently ignore the optional parameters and publicKey fields. We
* require that the parameters are encoded as part of the AlgorithmIdentifier,
* not in the private key structure.
*
* @since 1.6
* @author Andreas Sterbenz
*/
public final class ECPrivateKeyImpl extends PKCS8Key implements ECPrivateKey {
@java.io.Serial
private static final long serialVersionUID = 88695385615075129L;
private BigInteger s; // private value
private byte[] arrayS; // private value as a little-endian array
@SuppressWarnings("serial") // Type of field is not Serializable
private ECParameterSpec params;
private byte[] domainParams; //Currently unsupported
/**
* Construct a key from its encoding. Called by the ECKeyFactory.
*/
ECPrivateKeyImpl(byte[] encoded) throws InvalidKeyException {
super(encoded);
parseKeyBits();
}
/**
* Construct a key from its components. Used by the
* KeyFactory.
*/
ECPrivateKeyImpl(BigInteger s, ECParameterSpec params)
throws InvalidKeyException {
this.s = s;
this.params = params;
makeEncoding(s);
}
ECPrivateKeyImpl(byte[] s, ECParameterSpec params)
throws InvalidKeyException {
this.arrayS = s.clone();
this.params = params;
makeEncoding(s);
}
private void makeEncoding(byte[] s) throws InvalidKeyException {
algid = new AlgorithmId
(AlgorithmId.EC_oid, ECParameters.getAlgorithmParameters(params));
DerOutputStream out = new DerOutputStream();
out.putInteger(1); // version 1
byte[] privBytes = s.clone();
ArrayUtil.reverse(privBytes);
out.putOctetString(privBytes);
Arrays.fill(privBytes, (byte) 0);
DerValue val = DerValue.wrap(DerValue.tag_Sequence, out);
privKeyMaterial = val.toByteArray();
val.clear();
}
private void makeEncoding(BigInteger s) throws InvalidKeyException {
algid = new AlgorithmId(AlgorithmId.EC_oid,
ECParameters.getAlgorithmParameters(params));
byte[] sArr = s.toByteArray();
// convert to fixed-length array
int numOctets = (params.getOrder().bitLength() + 7) / 8;
byte[] sOctets = new byte[numOctets];
int inPos = Math.max(sArr.length - sOctets.length, 0);
int outPos = Math.max(sOctets.length - sArr.length, 0);
int length = Math.min(sArr.length, sOctets.length);
System.arraycopy(sArr, inPos, sOctets, outPos, length);
Arrays.fill(sArr, (byte) 0);
DerOutputStream out = new DerOutputStream();
out.putInteger(1); // version 1
out.putOctetString(sOctets);
Arrays.fill(sOctets, (byte) 0);
DerValue val = DerValue.wrap(DerValue.tag_Sequence, out);
privKeyMaterial = val.toByteArray();
val.clear();
}
// see JCA doc
public String getAlgorithm() {
return "EC";
}
// see JCA doc
public BigInteger getS() {
if (s == null) {
byte[] arrCopy = arrayS.clone();
ArrayUtil.reverse(arrCopy);
s = new BigInteger(1, arrCopy);
Arrays.fill(arrCopy, (byte)0);
}
return s;
}
// Return the internal arrayS byte[], if arrayS is null generate it.
public byte[] getArrayS() {
if (arrayS == null) {
arrayS = ECUtil.sArray(getS(), params);
}
return arrayS;
}
// see JCA doc
public ECParameterSpec getParams() {
return params;
}
/**
* Parse the ASN.1 of the privateKey Octet
*/
private void parseKeyBits() throws InvalidKeyException {
// Parse private key material from PKCS8Key.decode()
try {
DerInputStream in = new DerInputStream(privKeyMaterial);
DerValue derValue = in.getDerValue();
if (derValue.tag != DerValue.tag_Sequence) {
throw new IOException("Not a SEQUENCE");
}
DerInputStream data = derValue.data;
int version = data.getInteger();
if (version != V2) {
throw new IOException("Version must be 1");
}
byte[] privData = data.getOctetString();
ArrayUtil.reverse(privData);
arrayS = privData;
// Validate parameters stored from PKCS8Key.decode()
AlgorithmParameters algParams = this.algid.getParameters();
if (algParams == null) {
throw new InvalidKeyException("EC domain parameters must be "
+ "encoded in the algorithm identifier");
}
params = algParams.getParameterSpec(ECParameterSpec.class);
if (data.available() == 0) {
return;
}
DerValue value = data.getDerValue();
if (value.isContextSpecific((byte) 0)) {
domainParams = value.getDataBytes(); // Save DER sequence
if (data.available() == 0) {
return;
}
value = data.getDerValue();
}
if (value.isContextSpecific((byte) 1)) {
DerValue bits = value.withTag(DerValue.tag_BitString);
pubKeyEncoded = new X509Key(algid,
bits.data.getUnalignedBitString()).getEncoded();
} else {
throw new InvalidKeyException("Unexpected value: " + value);
}
} catch (IOException | InvalidParameterSpecException e) {
throw new InvalidKeyException("Invalid EC private key", e);
}
}
public PublicKey calculatePublicKey() {
ECParameterSpec ecParams = getParams();
ECOperations ops = ECOperations.forParameters(ecParams)
.orElseThrow(ProviderException::new);
MutablePoint pub = ops.multiply(ecParams.getGenerator(), getArrayS());
AffinePoint affPub = pub.asAffine();
ECPoint w = new ECPoint(affPub.getX().asBigInteger(),
affPub.getY().asBigInteger());
try {
return new ECPublicKeyImpl(w, ecParams);
} catch (InvalidKeyException e) {
throw new ProviderException(
"Unexpected error calculating public key", e);
}
}
/**
* Restores the state of this object from the stream.
* * Deserialization of this object is not supported. * * @param stream the {@code ObjectInputStream} from which data is read * @throws IOException if an I/O error occurs * @throws ClassNotFoundException if a serialized class cannot be loaded */ @java.io.Serial private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { throw new InvalidObjectException( "ECPrivateKeyImpl keys are not directly deserializable"); } }