diff options
| -rw-r--r-- | crypto/src/math/ec/multiplier/WNafUtilities.cs | 58 |
1 files changed, 38 insertions, 20 deletions
diff --git a/crypto/src/math/ec/multiplier/WNafUtilities.cs b/crypto/src/math/ec/multiplier/WNafUtilities.cs index b6e32382f..179d6d6eb 100644 --- a/crypto/src/math/ec/multiplier/WNafUtilities.cs +++ b/crypto/src/math/ec/multiplier/WNafUtilities.cs @@ -6,36 +6,42 @@ namespace Org.BouncyCastle.Math.EC.Multiplier { public static readonly string PRECOMP_NAME = "bc_wnaf"; - private static int[] DEFAULT_WINDOW_SIZE_CUTOFFS = new int[]{ 13, 41, 121, 337, 897, 2305 }; + private static readonly int[] DEFAULT_WINDOW_SIZE_CUTOFFS = new int[]{ 13, 41, 121, 337, 897, 2305 }; + + private static readonly byte[] EMPTY_BYTES = new byte[0]; + private static readonly int[] EMPTY_INTS = new int[0]; public static int[] GenerateCompactNaf(BigInteger k) { if ((k.BitLength >> 16) != 0) throw new ArgumentException("must have bitlength < 2^16", "k"); + if (k.SignValue == 0) + return EMPTY_INTS; BigInteger _3k = k.ShiftLeft(1).Add(k); - int digits = _3k.BitLength - 1; - int[] naf = new int[(digits + 1) >> 1]; + int bits = _3k.BitLength; + int[] naf = new int[bits >> 1]; - int length = 0, zeroes = 0; - for (int i = 1; i <= digits; ++i) - { - bool _3kBit = _3k.TestBit(i); - bool kBit = k.TestBit(i); + BigInteger diff = _3k.Xor(k); - if (_3kBit == kBit) + int highBit = bits - 1, length = 0, zeroes = 0; + for (int i = 1; i < highBit; ++i) + { + if (!diff.TestBit(i)) { ++zeroes; + continue; } - else - { - int digit = kBit ? -1 : 1; - naf[length++] = (digit << 16) | zeroes; - zeroes = 0; - } + + int digit = k.TestBit(i) ? -1 : 1; + naf[length++] = (digit << 16) | zeroes; + zeroes = 1; + ++i; } + naf[length++] = (1 << 16) | zeroes; + if (naf.Length > length) { naf = Trim(naf, length); @@ -55,6 +61,8 @@ namespace Org.BouncyCastle.Math.EC.Multiplier throw new ArgumentException("must be in the range [2, 16]", "width"); if ((k.BitLength >> 16) != 0) throw new ArgumentException("must have bitlength < 2^16", "k"); + if (k.SignValue == 0) + return EMPTY_INTS; int[] wnaf = new int[k.BitLength / width + 1]; @@ -166,19 +174,27 @@ namespace Org.BouncyCastle.Math.EC.Multiplier public static byte[] GenerateNaf(BigInteger k) { + if (k.SignValue == 0) + return EMPTY_BYTES; + BigInteger _3k = k.ShiftLeft(1).Add(k); int digits = _3k.BitLength - 1; byte[] naf = new byte[digits]; - for (int i = 1; i <= digits; ++i) - { - bool _3kBit = _3k.TestBit(i); - bool kBit = k.TestBit(i); + BigInteger diff = _3k.Xor(k); - naf[i - 1] = (byte)(_3kBit == kBit ? 0 : kBit ? -1 : 1); + for (int i = 1; i < digits; ++i) + { + if (diff.TestBit(i)) + { + naf[i - 1] = (byte)(k.TestBit(i) ? -1 : 1); + ++i; + } } + naf[digits - 1] = 1; + return naf; } @@ -203,6 +219,8 @@ namespace Org.BouncyCastle.Math.EC.Multiplier if (width < 2 || width > 8) throw new ArgumentException("must be in the range [2, 8]", "width"); + if (k.SignValue == 0) + return EMPTY_BYTES; byte[] wnaf = new byte[k.BitLength + 1]; |