/**
* Creates an elliptic curve characteristic 2 finite field which has 2^{@code m} elements with
* polynomial basis. The reduction polynomial for this field is based on {@code ks} whose content
* contains the order of the middle term(s) of the reduction polynomial. Note: A valid reduction
* polynomial is either a trinomial (X^{@code m} + X^{@code k} + 1 with {@code m} > {@code k}
* >= 1) or a pentanomial (X^{@code m} + X^{@code k3} + X^{@code k2} + X^{@code k1} + 1 with
* {@code m} > {@code k3} > {@code k2} > {@code k1} >= 1), so {@code ks} should have
* length 1 or 3.
*
* @param m with 2^{@code m} being the number of elements.
* @param ks the order of the middle term(s) of the reduction polynomial. Contents of this array
* are copied to protect against subsequent modification.
* @exception NullPointerException if {@code ks} is null.
* @exception IllegalArgumentException if{@code m} is not positive, or the length of {@code ks} is
* neither 1 nor 3, or values in {@code ks} are not between {@code m}-1 and 1 (inclusive) and
* in descending order.
*/
public ECFieldF2m(int m, int[] ks) {
// check m and ks
this.m = m;
this.ks = ks.clone();
if (m <= 0) {
throw new IllegalArgumentException("m is not positive");
}
if ((this.ks.length != 1) && (this.ks.length != 3)) {
throw new IllegalArgumentException("length of ks is neither 1 nor 3");
}
for (int i = 0; i < this.ks.length; i++) {
if ((this.ks[i] < 1) || (this.ks[i] > m - 1)) {
throw new IllegalArgumentException("ks[" + i + "] is out of range");
}
if ((i != 0) && (this.ks[i] >= this.ks[i - 1])) {
throw new IllegalArgumentException("values in ks are not in descending order");
}
}
// convert ks into rp
this.rp = BigInteger.ONE;
this.rp = rp.setBit(m);
for (int j = 0; j < this.ks.length; j++) {
rp = rp.setBit(this.ks[j]);
}
}
/**
* Encodes an APRep object.
*
* @return byte array of encoded APRep object.
* @exception Asn1Exception if an error occurs while decoding an ASN1 encoded data.
* @exception IOException if an I/O error occurs while reading encoded data.
*/
public byte[] asn1Encode() throws Asn1Exception, IOException {
DerOutputStream bytes = new DerOutputStream();
DerOutputStream temp = new DerOutputStream();
temp.putInteger(BigInteger.valueOf(pvno));
bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT, true, (byte) 0x00), temp);
temp = new DerOutputStream();
temp.putInteger(BigInteger.valueOf(msgType));
bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT, true, (byte) 0x01), temp);
bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT, true, (byte) 0x02), encPart.asn1Encode());
temp = new DerOutputStream();
temp.write(DerValue.tag_Sequence, bytes);
DerOutputStream aprep = new DerOutputStream();
aprep.write(DerValue.createTag(DerValue.TAG_APPLICATION, true, (byte) 0x0F), temp);
return aprep.toByteArray();
}
/**
* Returns a hash code value for this characteristic 2 finite field.
*
* @return a hash code value.
*/
public int hashCode() {
int value = m << 5;
value += (rp == null ? 0 : rp.hashCode());
// no need to involve ks here since ks and rp
// should be equivalent.
return value;
}
/**
* Creates an elliptic curve characteristic 2 finite field which has 2^{@code m} elements with
* polynomial basis. The reduction polynomial for this field is based on {@code rp} whose i-th bit
* corresponds to the i-th coefficient of the reduction polynomial.
*
* <p>Note: A valid reduction polynomial is either a trinomial (X^{@code m} + X^{@code k} + 1 with
* {@code m} > {@code k} >= 1) or a pentanomial (X^{@code m} + X^{@code k3} + X^{@code k2} +
* X^{@code k1} + 1 with {@code m} > {@code k3} > {@code k2} > {@code k1} >= 1).
*
* @param m with 2^{@code m} being the number of elements.
* @param rp the BigInteger whose i-th bit corresponds to the i-th coefficient of the reduction
* polynomial.
* @exception NullPointerException if {@code rp} is null.
* @exception IllegalArgumentException if {@code m} is not positive, or {@code rp} does not
* represent a valid reduction polynomial.
*/
public ECFieldF2m(int m, BigInteger rp) {
// check m and rp
this.m = m;
this.rp = rp;
if (m <= 0) {
throw new IllegalArgumentException("m is not positive");
}
int bitCount = this.rp.bitCount();
if (!this.rp.testBit(0) || !this.rp.testBit(m) || ((bitCount != 3) && (bitCount != 5))) {
throw new IllegalArgumentException("rp does not represent a valid reduction polynomial");
}
// convert rp into ks
BigInteger temp = this.rp.clearBit(0).clearBit(m);
this.ks = new int[bitCount - 2];
for (int i = this.ks.length - 1; i >= 0; i--) {
int index = temp.getLowestSetBit();
this.ks[i] = index;
temp = temp.clearBit(index);
}
}
/**
* Encodes a Checksum object. <xmp> Checksum ::= SEQUENCE { cksumtype [0] Int32, checksum [1]
* OCTET STRING } </xmp>
*
* <p>This definition reflects the Network Working Group RFC 4120 specification available at <a
* href="http://www.ietf.org/rfc/rfc4120.txt">http://www.ietf.org/rfc/rfc4120.txt</a>.
*
* @return byte array of enocded Checksum.
* @exception Asn1Exception if an error occurs while decoding an ASN1 encoded data.
* @exception IOException if an I/O error occurs while reading encoded data.
*/
public byte[] asn1Encode() throws Asn1Exception, IOException {
DerOutputStream bytes = new DerOutputStream();
DerOutputStream temp = new DerOutputStream();
temp.putInteger(BigInteger.valueOf(cksumType));
bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT, true, (byte) 0x00), temp);
temp = new DerOutputStream();
temp.putOctetString(checksum);
bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT, true, (byte) 0x01), temp);
temp = new DerOutputStream();
temp.write(DerValue.tag_Sequence, bytes);
return temp.toByteArray();
}
/** Construct a key from its components. Used by the KeyFactory. */
ECPrivateKeyImpl(BigInteger s, ECParameterSpec params) throws InvalidKeyException {
this.s = s;
this.params = params;
// generate the encoding
algid = new AlgorithmId(AlgorithmId.EC_oid, ECParameters.getAlgorithmParameters(params));
try {
DerOutputStream out = new DerOutputStream();
out.putInteger(1); // version 1
byte[] privBytes = ECUtil.trimZeroes(s.toByteArray());
out.putOctetString(privBytes);
DerValue val = new DerValue(DerValue.tag_Sequence, out.toByteArray());
key = val.toByteArray();
} catch (IOException exc) {
// should never occur
throw new InvalidKeyException(exc);
}
}
