package org.bouncycastle.crypto.prng.drbg;
import java.math.BigInteger;
import org.bouncycastle.asn1.nist.NISTNamedCurves;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.prng.EntropySource;
import org.bouncycastle.math.ec.ECCurve;
import org.bouncycastle.math.ec.ECMultiplier;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.math.ec.FixedPointCombMultiplier;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.BigIntegers;
/**
* A SP800-90A Dual EC DRBG.
*/
public class DualECSP800DRBG
implements SP80090DRBG
{
/*
* Default P, Q values for each curve
*/
private static final BigInteger p256_Px = new BigInteger("6b17d1f2e12c4247f8bce6e563a440f277037d812deb33a0f4a13945d898c296", 16);
private static final BigInteger p256_Py = new BigInteger("4fe342e2fe1a7f9b8ee7eb4a7c0f9e162bce33576b315ececbb6406837bf51f5", 16);
private static final BigInteger p256_Qx = new BigInteger("c97445f45cdef9f0d3e05e1e585fc297235b82b5be8ff3efca67c59852018192", 16);
private static final BigInteger p256_Qy = new BigInteger("b28ef557ba31dfcbdd21ac46e2a91e3c304f44cb87058ada2cb815151e610046", 16);
private static final BigInteger p384_Px = new BigInteger("aa87ca22be8b05378eb1c71ef320ad746e1d3b628ba79b9859f741e082542a385502f25dbf55296c3a545e3872760ab7", 16);
private static final BigInteger p384_Py = new BigInteger("3617de4a96262c6f5d9e98bf9292dc29f8f41dbd289a147ce9da3113b5f0b8c00a60b1ce1d7e819d7a431d7c90ea0e5f", 16);
private static final BigInteger p384_Qx = new BigInteger("8e722de3125bddb05580164bfe20b8b432216a62926c57502ceede31c47816edd1e89769124179d0b695106428815065", 16);
private static final BigInteger p384_Qy = new BigInteger("023b1660dd701d0839fd45eec36f9ee7b32e13b315dc02610aa1b636e346df671f790f84c5e09b05674dbb7e45c803dd", 16);
private static final BigInteger p521_Px = new BigInteger("c6858e06b70404e9cd9e3ecb662395b4429c648139053fb521f828af606b4d3dbaa14b5e77efe75928fe1dc127a2ffa8de3348b3c1856a429bf97e7e31c2e5bd66", 16);
private static final BigInteger p521_Py = new BigInteger("11839296a789a3bc0045c8a5fb42c7d1bd998f54449579b446817afbd17273e662c97ee72995ef42640c550b9013fad0761353c7086a272c24088be94769fd16650", 16);
private static final BigInteger p521_Qx = new BigInteger("1b9fa3e518d683c6b65763694ac8efbaec6fab44f2276171a42726507dd08add4c3b3f4c1ebc5b1222ddba077f722943b24c3edfa0f85fe24d0c8c01591f0be6f63", 16);
private static final BigInteger p521_Qy = new BigInteger("1f3bdba585295d9a1110d1df1f9430ef8442c5018976ff3437ef91b81dc0b8132c8d5c39c32d0e004a3092b7d327c0e7a4d26d2c7b69b58f9066652911e457779de", 16);
private static final DualECPoints[] nistPoints;
static
{
nistPoints = new DualECPoints[3];
ECCurve.Fp curve = (ECCurve.Fp)NISTNamedCurves.getByName("P-256").getCurve();
nistPoints[0] = new DualECPoints(128, curve.createPoint(p256_Px, p256_Py), curve.createPoint(p256_Qx, p256_Qy), 1);
curve = (ECCurve.Fp)NISTNamedCurves.getByName("P-384").getCurve();
nistPoints[1] = new DualECPoints(192, curve.createPoint(p384_Px, p384_Py), curve.createPoint(p384_Qx, p384_Qy), 1);
curve = (ECCurve.Fp)NISTNamedCurves.getByName("P-521").getCurve();
nistPoints[2] = new DualECPoints(256, curve.createPoint(p521_Px, p521_Py), curve.createPoint(p521_Qx, p521_Qy), 1);
}
private static final long RESEED_MAX = 1L << (32 - 1);
private static final int MAX_ADDITIONAL_INPUT = 1 << (13 - 1);
private static final int MAX_ENTROPY_LENGTH = 1 << (13 - 1);
private static final int MAX_PERSONALIZATION_STRING = 1 << (13 -1);
private Digest _digest;
private long _reseedCounter;
private EntropySource _entropySource;
private int _securityStrength;
private int _seedlen;
private int _outlen;
private ECCurve.Fp _curve;
private ECPoint _P;
private ECPoint _Q;
private byte[] _s;
private int _sLength;
private ECMultiplier _fixedPointMultiplier = new FixedPointCombMultiplier();
/**
* Construct a SP800-90A Dual EC DRBG.
* <p>
* Minimum entropy requirement is the security strength requested.
* </p>
* @param digest source digest to use with the DRB stream.
* @param securityStrength security strength required (in bits)
* @param entropySource source of entropy to use for seeding/reseeding.
* @param personalizationString personalization string to distinguish this DRBG (may be null).
* @param nonce nonce to further distinguish this DRBG (may be null).
*/
public DualECSP800DRBG(Digest digest, int securityStrength, EntropySource entropySource, byte[] personalizationString, byte[] nonce)
{
this(nistPoints, digest, securityStrength, entropySource, personalizationString, nonce);
}
/**
* Construct a SP800-90A Dual EC DRBG.
* <p>
* Minimum entropy requirement is the security strength requested.
* </p>
* @param pointSet an array of points to choose from, in order of increasing security strength
* @param digest source digest to use with the DRB stream.
* @param securityStrength security strength required (in bits)
* @param entropySource source of entropy to use for seeding/reseeding.
* @param personalizationString personalization string to distinguish this DRBG (may be null).
* @param nonce nonce to further distinguish this DRBG (may be null).
*/
public DualECSP800DRBG(DualECPoints[] pointSet, Digest digest, int securityStrength, EntropySource entropySource, byte[] personalizationString, byte[] nonce)
{
_digest = digest;
_entropySource = entropySource;
_securityStrength = securityStrength;
if (Utils.isTooLarge(personalizationString, MAX_PERSONALIZATION_STRING / 8))
{
throw new IllegalArgumentException("Personalization string too large");
}
if (entropySource.entropySize() < securityStrength || entropySource.entropySize() > MAX_ENTROPY_LENGTH)
{
throw new IllegalArgumentException("EntropySource must provide between " + securityStrength + " and " + MAX_ENTROPY_LENGTH + " bits");
}
byte[] entropy = getEntropy();
byte[] seedMaterial = Arrays.concatenate(entropy, nonce, personalizationString);
for (int i = 0; i != pointSet.length; i++)
{
if (securityStrength <= pointSet[i].getSecurityStrength())
{
if (Utils.getMaxSecurityStrength(digest) < pointSet[i].getSecurityStrength())
{
throw new IllegalArgumentException("Requested security strength is not supported by digest");
}
_seedlen = pointSet[i].getSeedLen();
_outlen = pointSet[i].getMaxOutlen() / 8;
_P = pointSet[i].getP();
_Q = pointSet[i].getQ();
break;
}
}
if (_P == null)
{
throw new IllegalArgumentException("security strength cannot be greater than 256 bits");
}
_s = Utils.hash_df(_digest, seedMaterial, _seedlen);
_sLength = _s.length;
_reseedCounter = 0;
}
/**
* Return the block size (in bits) of the DRBG.
*
* @return the number of bits produced on each internal round of the DRBG.
*/
public int getBlockSize()
{
return _outlen * 8;
}
/**
* Populate a passed in array with random data.
*
* @param output output array for generated bits.
* @param additionalInput additional input to be added to the DRBG in this step.
* @param predictionResistant true if a reseed should be forced, false otherwise.
*
* @return number of bits generated, -1 if a reseed required.
*/
public int generate(byte[] output, byte[] additionalInput, boolean predictionResistant)
{
int numberOfBits = output.length*8;
int m = output.length / _outlen;
if (Utils.isTooLarge(additionalInput, MAX_ADDITIONAL_INPUT / 8))
{
throw new IllegalArgumentException("Additional input too large");
}
if (_reseedCounter + m > RESEED_MAX)
{
return -1;
}
if (predictionResistant)
{
reseed(additionalInput);
additionalInput = null;
}
BigInteger s;
if (additionalInput != null)
{
// Note: we ignore the use of pad8 on the additional input as we mandate byte arrays for it.
additionalInput = Utils.hash_df(_digest, additionalInput, _seedlen);
s = new BigInteger(1, xor(_s, additionalInput));
}
else
{
s = new BigInteger(1, _s);
}
// make sure we start with a clean output array.
Arrays.fill(output, (byte)0);
int outOffset = 0;
for (int i = 0; i < m; i++)
{
s = getScalarMultipleXCoord(_P, s);
//System.err.println("S: " + new String(Hex.encode(_s)));
byte[] r = getScalarMultipleXCoord(_Q, s).toByteArray();
if (r.length > _outlen)
{
System.arraycopy(r, r.length - _outlen, output, outOffset, _outlen);
}
else
{
System.arraycopy(r, 0, output, outOffset + (_outlen - r.length), r.length);
}
//System.err.println("R: " + new String(Hex.encode(r)));
outOffset += _outlen;
_reseedCounter++;
}
if (outOffset < output.length)
{
s = getScalarMultipleXCoord(_P, s);
byte[] r = getScalarMultipleXCoord(_Q, s).toByteArray();
int required = output.length - outOffset;
if (r.length > _outlen)
{
System.arraycopy(r, r.length - _outlen, output, outOffset, required);
}
else
{
System.arraycopy(r, 0, output, outOffset + (_outlen - r.length), required);
}
_reseedCounter++;
}
// Need to preserve length of S as unsigned int.
_s = BigIntegers.asUnsignedByteArray(_sLength, getScalarMultipleXCoord(_P, s));
return numberOfBits;
}
/**
* Reseed the DRBG.
*
* @param additionalInput additional input to be added to the DRBG in this step.
*/
public void reseed(byte[] additionalInput)
{
if (Utils.isTooLarge(additionalInput, MAX_ADDITIONAL_INPUT / 8))
{
throw new IllegalArgumentException("Additional input string too large");
}
byte[] entropy = getEntropy();
byte[] seedMaterial = Arrays.concatenate(pad8(_s, _seedlen), entropy, additionalInput);
_s = Utils.hash_df(_digest, seedMaterial, _seedlen);
_reseedCounter = 0;
}
private byte[] getEntropy()
{
byte[] entropy = _entropySource.getEntropy();
if (entropy.length < (_securityStrength + 7) / 8)
{
throw new IllegalStateException("Insufficient entropy provided by entropy source");
}
return entropy;
}
private byte[] xor(byte[] a, byte[] b)
{
if (b == null)
{
return a;
}
byte[] rv = new byte[a.length];
for (int i = 0; i != rv.length; i++)
{
rv[i] = (byte)(a[i] ^ b[i]);
}
return rv;
}
// Note: works in place
private byte[] pad8(byte[] s, int seedlen)
{
if (seedlen % 8 == 0)
{
return s;
}
int shift = 8 - (seedlen % 8);
int carry = 0;
for (int i = s.length - 1; i >= 0; i--)
{
int b = s[i] & 0xff;
s[i] = (byte)((b << shift) | (carry >> (8 - shift)));
carry = b;
}
return s;
}
private BigInteger getScalarMultipleXCoord(ECPoint p, BigInteger s)
{
return _fixedPointMultiplier.multiply(p, s).normalize().getAffineXCoord().toBigInteger();
}
}