org.bouncycastle.crypto.generators.DSAParametersGenerator Maven / Gradle / Ivy
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package org.bouncycastle.crypto.generators;
import java.math.BigInteger;
import java.security.SecureRandom;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.digests.SHA1Digest;
import org.bouncycastle.crypto.params.DSAParameterGenerationParameters;
import org.bouncycastle.crypto.params.DSAParameters;
import org.bouncycastle.crypto.params.DSAValidationParameters;
import org.bouncycastle.crypto.util.DigestFactory;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.BigIntegers;
import org.bouncycastle.util.encoders.Hex;
/**
* Generate suitable parameters for DSA, in line with FIPS 186-2, or FIPS 186-3.
*/
public class DSAParametersGenerator
{
private static final BigInteger ZERO = BigInteger.valueOf(0);
private static final BigInteger ONE = BigInteger.valueOf(1);
private static final BigInteger TWO = BigInteger.valueOf(2);
private Digest digest;
private int L, N;
private int certainty;
private int iterations;
private SecureRandom random;
private boolean use186_3;
private int usageIndex;
public DSAParametersGenerator()
{
this(DigestFactory.createSHA1());
}
public DSAParametersGenerator(Digest digest)
{
this.digest = digest;
}
/**
* initialise the key generator.
*
* @param size size of the key (range 2^512 -> 2^1024 - 64 bit increments)
* @param certainty measure of robustness of prime (for FIPS 186-2 compliance this should be at least 80).
* @param random random byte source.
*/
public void init(
int size,
int certainty,
SecureRandom random)
{
this.L = size;
this.N = getDefaultN(size);
this.certainty = certainty;
this.iterations = Math.max(getMinimumIterations(L), (certainty + 1) / 2);
this.random = random;
this.use186_3 = false;
this.usageIndex = -1;
}
/**
* Initialise the key generator for DSA 2.
*
* Use this init method if you need to generate parameters for DSA 2 keys.
*
*
* @param params DSA 2 key generation parameters.
*/
public void init(
DSAParameterGenerationParameters params)
{
int L = params.getL(), N = params.getN();
if ((L < 1024 || L > 3072) || L % 1024 != 0)
{
throw new IllegalArgumentException("L values must be between 1024 and 3072 and a multiple of 1024");
}
else if (L == 1024 && N != 160)
{
throw new IllegalArgumentException("N must be 160 for L = 1024");
}
else if (L == 2048 && (N != 224 && N != 256))
{
throw new IllegalArgumentException("N must be 224 or 256 for L = 2048");
}
else if (L == 3072 && N != 256)
{
throw new IllegalArgumentException("N must be 256 for L = 3072");
}
if (digest.getDigestSize() * 8 < N)
{
throw new IllegalStateException("Digest output size too small for value of N");
}
this.L = L;
this.N = N;
this.certainty = params.getCertainty();
this.iterations = Math.max(getMinimumIterations(L), (certainty + 1) / 2);
this.random = params.getRandom();
this.use186_3 = true;
this.usageIndex = params.getUsageIndex();
}
/**
* which generates the p and g values from the given parameters,
* returning the DSAParameters object.
*
* Note: can take a while...
* @return a generated DSA parameters object.
*/
public DSAParameters generateParameters()
{
return (use186_3)
? generateParameters_FIPS186_3()
: generateParameters_FIPS186_2();
}
private DSAParameters generateParameters_FIPS186_2()
{
byte[] seed = new byte[20];
byte[] part1 = new byte[20];
byte[] part2 = new byte[20];
byte[] u = new byte[20];
int n = (L - 1) / 160;
byte[] w = new byte[L / 8];
if (!(digest instanceof SHA1Digest))
{
throw new IllegalStateException("can only use SHA-1 for generating FIPS 186-2 parameters");
}
for (;;)
{
random.nextBytes(seed);
hash(digest, seed, part1, 0);
System.arraycopy(seed, 0, part2, 0, seed.length);
inc(part2);
hash(digest, part2, part2, 0);
for (int i = 0; i != u.length; i++)
{
u[i] = (byte)(part1[i] ^ part2[i]);
}
u[0] |= (byte)0x80;
u[19] |= (byte)0x01;
BigInteger q = new BigInteger(1, u);
if (!isProbablePrime(q))
{
continue;
}
byte[] offset = Arrays.clone(seed);
inc(offset);
for (int counter = 0; counter < 4096; ++counter)
{
{
for (int k = 1; k <= n; k++)
{
inc(offset);
hash(digest, offset, w, w.length - k * part1.length);
}
int remaining = w.length - (n * part1.length);
inc(offset);
hash(digest, offset, part1, 0);
System.arraycopy(part1, part1.length - remaining, w, 0, remaining);
w[0] |= (byte)0x80;
}
BigInteger x = new BigInteger(1, w);
BigInteger c = x.mod(q.shiftLeft(1));
BigInteger p = x.subtract(c.subtract(ONE));
if (p.bitLength() != L)
{
continue;
}
if (isProbablePrime(p))
{
BigInteger g = calculateGenerator_FIPS186_2(p, q, random);
return new DSAParameters(p, q, g, new DSAValidationParameters(seed, counter));
}
}
}
}
private static BigInteger calculateGenerator_FIPS186_2(BigInteger p, BigInteger q, SecureRandom r)
{
BigInteger e = p.subtract(ONE).divide(q);
BigInteger pSub2 = p.subtract(TWO);
for (;;)
{
BigInteger h = BigIntegers.createRandomInRange(TWO, pSub2, r);
BigInteger g = h.modPow(e, p);
if (g.bitLength() > 1)
{
return g;
}
}
}
/**
* generate suitable parameters for DSA, in line with
* FIPS 186-3 A.1 Generation of the FFC Primes p and q.
*/
private DSAParameters generateParameters_FIPS186_3()
{
// A.1.1.2 Generation of the Probable Primes p and q Using an Approved Hash Function
// FIXME This should be configurable (digest size in bits must be >= N)
Digest d = digest;
int outlen = d.getDigestSize() * 8;
// 1. Check that the (L, N) pair is in the list of acceptable (L, N pairs) (see Section 4.2). If
// the pair is not in the list, then return INVALID.
// Note: checked at initialisation
// 2. If (seedlen < N), then return INVALID.
// FIXME This should be configurable (must be >= N)
int seedlen = N;
byte[] seed = new byte[seedlen / 8];
// 3. n = ceiling(L / outlen) - 1.
int n = (L - 1) / outlen;
// 4. b = L - 1 - (n * outlen).
int b = (L - 1) % outlen;
byte[] w = new byte[L / 8];
byte[] output = new byte[d.getDigestSize()];
for (;;)
{
// 5. Get an arbitrary sequence of seedlen bits as the domain_parameter_seed.
random.nextBytes(seed);
// 6. U = Hash (domain_parameter_seed) mod 2^(N–1).
hash(d, seed, output, 0);
BigInteger U = new BigInteger(1, output).mod(ONE.shiftLeft(N - 1));
// 7. q = 2^(N–1) + U + 1 – ( U mod 2).
BigInteger q = U.setBit(0).setBit(N - 1);
// 8. Test whether or not q is prime as specified in Appendix C.3.
if (!isProbablePrime(q))
{
// 9. If q is not a prime, then go to step 5.
continue;
}
// 10. offset = 1.
// Note: 'offset' value managed incrementally
byte[] offset = Arrays.clone(seed);
// 11. For counter = 0 to (4L – 1) do
int counterLimit = 4 * L;
for (int counter = 0; counter < counterLimit; ++counter)
{
// 11.1 For j = 0 to n do
// Vj = Hash ((domain_parameter_seed + offset + j) mod 2^seedlen).
// 11.2 W = V0 + (V1 ∗ 2^outlen) + ... + (V^(n–1) ∗ 2^((n–1) ∗ outlen)) + ((Vn mod 2^b) ∗ 2^(n ∗ outlen)).
{
for (int j = 1; j <= n; ++j)
{
inc(offset);
hash(d, offset, w, w.length - j * output.length);
}
int remaining = w.length - (n * output.length);
inc(offset);
hash(d, offset, output, 0);
System.arraycopy(output, output.length - remaining, w, 0, remaining);
// 11.3 X = W + 2^(L–1). Comment: 0 ≤ W < 2^(L–1); hence, 2^(L–1) ≤ X < 2^L.
w[0] |= (byte)0x80;
}
BigInteger X = new BigInteger(1, w);
// 11.4 c = X mod 2q.
BigInteger c = X.mod(q.shiftLeft(1));
// 11.5 p = X - (c - 1). Comment: p ≡ 1 (mod 2q).
BigInteger p = X.subtract(c.subtract(ONE));
// 11.6 If (p < 2^(L-1)), then go to step 11.9
if (p.bitLength() != L)
{
continue;
}
// 11.7 Test whether or not p is prime as specified in Appendix C.3.
if (isProbablePrime(p))
{
// 11.8 If p is determined to be prime, then return VALID and the values of p, q and
// (optionally) the values of domain_parameter_seed and counter.
if (usageIndex >= 0)
{
BigInteger g = calculateGenerator_FIPS186_3_Verifiable(d, p, q, seed, usageIndex);
if (g != null)
{
return new DSAParameters(p, q, g, new DSAValidationParameters(seed, counter, usageIndex));
}
}
BigInteger g = calculateGenerator_FIPS186_3_Unverifiable(p, q, random);
return new DSAParameters(p, q, g, new DSAValidationParameters(seed, counter));
}
// 11.9 offset = offset + n + 1. Comment: Increment offset; then, as part of
// the loop in step 11, increment counter; if
// counter < 4L, repeat steps 11.1 through 11.8.
// Note: 'offset' value already incremented in inner loop
}
// 12. Go to step 5.
}
}
private boolean isProbablePrime(BigInteger x)
{
/*
* TODO Use Primes class for FIPS 186-4 C.3 primality checking - but it breaks existing
* tests using FixedSecureRandom
*/
// return !Primes.hasAnySmallFactors(x) && Primes.isMRProbablePrime(x, random, iterations);
return x.isProbablePrime(certainty);
}
private static BigInteger calculateGenerator_FIPS186_3_Unverifiable(BigInteger p, BigInteger q,
SecureRandom r)
{
return calculateGenerator_FIPS186_2(p, q, r);
}
private static BigInteger calculateGenerator_FIPS186_3_Verifiable(Digest d, BigInteger p, BigInteger q,
byte[] seed, int index)
{
// A.2.3 Verifiable Canonical Generation of the Generator g
BigInteger e = p.subtract(ONE).divide(q);
byte[] ggen = Hex.decodeStrict("6767656E");
// 7. U = domain_parameter_seed || "ggen" || index || count.
byte[] U = new byte[seed.length + ggen.length + 1 + 2];
System.arraycopy(seed, 0, U, 0, seed.length);
System.arraycopy(ggen, 0, U, seed.length, ggen.length);
U[U.length - 3] = (byte)index;
byte[] w = new byte[d.getDigestSize()];
for (int count = 1; count < (1 << 16); ++count)
{
inc(U);
hash(d, U, w, 0);
BigInteger W = new BigInteger(1, w);
BigInteger g = W.modPow(e, p);
if (g.compareTo(TWO) >= 0)
{
return g;
}
}
return null;
}
private static void hash(Digest d, byte[] input, byte[] output, int outputPos)
{
d.update(input, 0, input.length);
d.doFinal(output, outputPos);
}
private static int getDefaultN(int L)
{
return L > 1024 ? 256 : 160;
}
private static int getMinimumIterations(int L)
{
// Values based on FIPS 186-4 C.3 Table C.1
return L <= 1024 ? 40 : (48 + 8 * ((L - 1) / 1024));
}
private static void inc(byte[] buf)
{
for (int i = buf.length - 1; i >= 0; --i)
{
byte b = (byte)((buf[i] + 1) & 0xff);
buf[i] = b;
if (b != 0)
{
break;
}
}
}
}