http://www.bouncycastle.org/java.html: The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5. 
public class org.bouncycastle.crypto.signers.ECDSASigner implements org.bouncycastle.math.ec.ECConstants, org.bouncycastle.crypto.DSA
  minor version: 0
  major version: 59
  flags: flags: (0x0021) ACC_PUBLIC, ACC_SUPER
  this_class: org.bouncycastle.crypto.signers.ECDSASigner
  super_class: java.lang.Object
{
  org.bouncycastle.crypto.params.ECKeyParameters key;
    descriptor: Lorg/bouncycastle/crypto/params/ECKeyParameters;
    flags: (0x0000) 

  java.security.SecureRandom random;
    descriptor: Ljava/security/SecureRandom;
    flags: (0x0000) 

  public void <init>();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
         0: .line 19
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/bouncycastle/crypto/signers/ECDSASigner;

  public void init(boolean, org.bouncycastle.crypto.CipherParameters);
    descriptor: (ZLorg/bouncycastle/crypto/CipherParameters;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=4, args_size=3
        start local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
        start local 1 // boolean forSigning
        start local 2 // org.bouncycastle.crypto.CipherParameters param
         0: .line 30
            iload 1 /* forSigning */
            ifeq 9
         1: .line 32
            aload 2 /* param */
            instanceof org.bouncycastle.crypto.params.ParametersWithRandom
            ifeq 6
         2: .line 34
            aload 2 /* param */
            checkcast org.bouncycastle.crypto.params.ParametersWithRandom
            astore 3 /* rParam */
        start local 3 // org.bouncycastle.crypto.params.ParametersWithRandom rParam
         3: .line 36
            aload 0 /* this */
            aload 3 /* rParam */
            invokevirtual org.bouncycastle.crypto.params.ParametersWithRandom.getRandom:()Ljava/security/SecureRandom;
            putfield org.bouncycastle.crypto.signers.ECDSASigner.random:Ljava/security/SecureRandom;
         4: .line 37
            aload 0 /* this */
            aload 3 /* rParam */
            invokevirtual org.bouncycastle.crypto.params.ParametersWithRandom.getParameters:()Lorg/bouncycastle/crypto/CipherParameters;
            checkcast org.bouncycastle.crypto.params.ECPrivateKeyParameters
            putfield org.bouncycastle.crypto.signers.ECDSASigner.key:Lorg/bouncycastle/crypto/params/ECKeyParameters;
        end local 3 // org.bouncycastle.crypto.params.ParametersWithRandom rParam
         5: .line 38
            goto 10
         6: .line 41
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            new java.security.SecureRandom
            dup
            invokespecial java.security.SecureRandom.<init>:()V
            putfield org.bouncycastle.crypto.signers.ECDSASigner.random:Ljava/security/SecureRandom;
         7: .line 42
            aload 0 /* this */
            aload 2 /* param */
            checkcast org.bouncycastle.crypto.params.ECPrivateKeyParameters
            putfield org.bouncycastle.crypto.signers.ECDSASigner.key:Lorg/bouncycastle/crypto/params/ECKeyParameters;
         8: .line 44
            goto 10
         9: .line 47
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            aload 2 /* param */
            checkcast org.bouncycastle.crypto.params.ECPublicKeyParameters
            putfield org.bouncycastle.crypto.signers.ECDSASigner.key:Lorg/bouncycastle/crypto/params/ECKeyParameters;
        10: .line 49
      StackMap locals:
      StackMap stack:
            return
        end local 2 // org.bouncycastle.crypto.CipherParameters param
        end local 1 // boolean forSigning
        end local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
      LocalVariableTable:
        Start  End  Slot        Name  Signature
            0   11     0        this  Lorg/bouncycastle/crypto/signers/ECDSASigner;
            0   11     1  forSigning  Z
            0   11     2       param  Lorg/bouncycastle/crypto/CipherParameters;
            3    5     3      rParam  Lorg/bouncycastle/crypto/params/ParametersWithRandom;
    MethodParameters:
            Name  Flags
      forSigning  
      param       

  public java.math.BigInteger[] generateSignature(byte[]);
    descriptor: ([B)[Ljava/math/BigInteger;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=4, locals=10, args_size=2
        start local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
        start local 1 // byte[] message
         0: .line 62
            aload 0 /* this */
            getfield org.bouncycastle.crypto.signers.ECDSASigner.key:Lorg/bouncycastle/crypto/params/ECKeyParameters;
            invokevirtual org.bouncycastle.crypto.params.ECKeyParameters.getParameters:()Lorg/bouncycastle/crypto/params/ECDomainParameters;
            invokevirtual org.bouncycastle.crypto.params.ECDomainParameters.getN:()Ljava/math/BigInteger;
            astore 2 /* n */
        start local 2 // java.math.BigInteger n
         1: .line 63
            aload 0 /* this */
            aload 2 /* n */
            aload 1 /* message */
            invokevirtual org.bouncycastle.crypto.signers.ECDSASigner.calculateE:(Ljava/math/BigInteger;[B)Ljava/math/BigInteger;
            astore 3 /* e */
        start local 3 // java.math.BigInteger e
         2: .line 64
            aconst_null
            astore 4 /* r */
        start local 4 // java.math.BigInteger r
         3: .line 65
            aconst_null
            astore 5 /* s */
        start local 5 // java.math.BigInteger s
         4: .line 70
      StackMap locals: org.bouncycastle.crypto.signers.ECDSASigner byte[] java.math.BigInteger java.math.BigInteger java.math.BigInteger java.math.BigInteger
      StackMap stack:
            aconst_null
            astore 6 /* k */
        start local 6 // java.math.BigInteger k
         5: .line 71
            aload 2 /* n */
            invokevirtual java.math.BigInteger.bitLength:()I
            istore 7 /* nBitLength */
        start local 7 // int nBitLength
         6: .line 77
      StackMap locals: java.math.BigInteger int
      StackMap stack:
            new java.math.BigInteger
            dup
            iload 7 /* nBitLength */
            aload 0 /* this */
            getfield org.bouncycastle.crypto.signers.ECDSASigner.random:Ljava/security/SecureRandom;
            invokespecial java.math.BigInteger.<init>:(ILjava/util/Random;)V
            astore 6 /* k */
         7: .line 79
            aload 6 /* k */
            getstatic org.bouncycastle.crypto.signers.ECDSASigner.ZERO:Ljava/math/BigInteger;
            invokevirtual java.math.BigInteger.equals:(Ljava/lang/Object;)Z
            ifne 6
            aload 6 /* k */
            aload 2 /* n */
            invokevirtual java.math.BigInteger.compareTo:(Ljava/math/BigInteger;)I
         8: .line 75
            ifge 6
         9: .line 81
            aload 0 /* this */
            getfield org.bouncycastle.crypto.signers.ECDSASigner.key:Lorg/bouncycastle/crypto/params/ECKeyParameters;
            invokevirtual org.bouncycastle.crypto.params.ECKeyParameters.getParameters:()Lorg/bouncycastle/crypto/params/ECDomainParameters;
            invokevirtual org.bouncycastle.crypto.params.ECDomainParameters.getG:()Lorg/bouncycastle/math/ec/ECPoint;
            aload 6 /* k */
            invokevirtual org.bouncycastle.math.ec.ECPoint.multiply:(Ljava/math/BigInteger;)Lorg/bouncycastle/math/ec/ECPoint;
            astore 8 /* p */
        start local 8 // org.bouncycastle.math.ec.ECPoint p
        10: .line 84
            aload 8 /* p */
            invokevirtual org.bouncycastle.math.ec.ECPoint.getX:()Lorg/bouncycastle/math/ec/ECFieldElement;
            invokevirtual org.bouncycastle.math.ec.ECFieldElement.toBigInteger:()Ljava/math/BigInteger;
            astore 9 /* x */
        start local 9 // java.math.BigInteger x
        11: .line 86
            aload 9 /* x */
            aload 2 /* n */
            invokevirtual java.math.BigInteger.mod:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            astore 4 /* r */
        end local 9 // java.math.BigInteger x
        end local 8 // org.bouncycastle.math.ec.ECPoint p
        12: .line 88
            aload 4 /* r */
            getstatic org.bouncycastle.crypto.signers.ECDSASigner.ZERO:Ljava/math/BigInteger;
            invokevirtual java.math.BigInteger.equals:(Ljava/lang/Object;)Z
            ifne 6
        13: .line 90
            aload 0 /* this */
            getfield org.bouncycastle.crypto.signers.ECDSASigner.key:Lorg/bouncycastle/crypto/params/ECKeyParameters;
            checkcast org.bouncycastle.crypto.params.ECPrivateKeyParameters
            invokevirtual org.bouncycastle.crypto.params.ECPrivateKeyParameters.getD:()Ljava/math/BigInteger;
            astore 8 /* d */
        start local 8 // java.math.BigInteger d
        14: .line 92
            aload 6 /* k */
            aload 2 /* n */
            invokevirtual java.math.BigInteger.modInverse:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            aload 3 /* e */
            aload 8 /* d */
            aload 4 /* r */
            invokevirtual java.math.BigInteger.multiply:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            invokevirtual java.math.BigInteger.add:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            invokevirtual java.math.BigInteger.multiply:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            aload 2 /* n */
            invokevirtual java.math.BigInteger.mod:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            astore 5 /* s */
        end local 8 // java.math.BigInteger d
        end local 7 // int nBitLength
        end local 6 // java.math.BigInteger k
        15: .line 94
            aload 5 /* s */
            getstatic org.bouncycastle.crypto.signers.ECDSASigner.ZERO:Ljava/math/BigInteger;
            invokevirtual java.math.BigInteger.equals:(Ljava/lang/Object;)Z
            ifne 4
        16: .line 96
            iconst_2
            anewarray java.math.BigInteger
            astore 6 /* res */
        start local 6 // java.math.BigInteger[] res
        17: .line 98
            aload 6 /* res */
            iconst_0
            aload 4 /* r */
            aastore
        18: .line 99
            aload 6 /* res */
            iconst_1
            aload 5 /* s */
            aastore
        19: .line 101
            aload 6 /* res */
            areturn
        end local 6 // java.math.BigInteger[] res
        end local 5 // java.math.BigInteger s
        end local 4 // java.math.BigInteger r
        end local 3 // java.math.BigInteger e
        end local 2 // java.math.BigInteger n
        end local 1 // byte[] message
        end local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
      LocalVariableTable:
        Start  End  Slot        Name  Signature
            0   20     0        this  Lorg/bouncycastle/crypto/signers/ECDSASigner;
            0   20     1     message  [B
            1   20     2           n  Ljava/math/BigInteger;
            2   20     3           e  Ljava/math/BigInteger;
            3   20     4           r  Ljava/math/BigInteger;
            4   20     5           s  Ljava/math/BigInteger;
            5   15     6           k  Ljava/math/BigInteger;
            6   15     7  nBitLength  I
           10   12     8           p  Lorg/bouncycastle/math/ec/ECPoint;
           11   12     9           x  Ljava/math/BigInteger;
           14   15     8           d  Ljava/math/BigInteger;
           17   20     6         res  [Ljava/math/BigInteger;
    MethodParameters:
         Name  Flags
      message  

  public boolean verifySignature(byte[], java.math.BigInteger, java.math.BigInteger);
    descriptor: ([BLjava/math/BigInteger;Ljava/math/BigInteger;)Z
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=4, locals=13, args_size=4
        start local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
        start local 1 // byte[] message
        start local 2 // java.math.BigInteger r
        start local 3 // java.math.BigInteger s
         0: .line 115
            aload 0 /* this */
            getfield org.bouncycastle.crypto.signers.ECDSASigner.key:Lorg/bouncycastle/crypto/params/ECKeyParameters;
            invokevirtual org.bouncycastle.crypto.params.ECKeyParameters.getParameters:()Lorg/bouncycastle/crypto/params/ECDomainParameters;
            invokevirtual org.bouncycastle.crypto.params.ECDomainParameters.getN:()Ljava/math/BigInteger;
            astore 4 /* n */
        start local 4 // java.math.BigInteger n
         1: .line 116
            aload 0 /* this */
            aload 4 /* n */
            aload 1 /* message */
            invokevirtual org.bouncycastle.crypto.signers.ECDSASigner.calculateE:(Ljava/math/BigInteger;[B)Ljava/math/BigInteger;
            astore 5 /* e */
        start local 5 // java.math.BigInteger e
         2: .line 119
            aload 2 /* r */
            getstatic org.bouncycastle.crypto.signers.ECDSASigner.ONE:Ljava/math/BigInteger;
            invokevirtual java.math.BigInteger.compareTo:(Ljava/math/BigInteger;)I
            iflt 3
            aload 2 /* r */
            aload 4 /* n */
            invokevirtual java.math.BigInteger.compareTo:(Ljava/math/BigInteger;)I
            iflt 4
         3: .line 121
      StackMap locals: java.math.BigInteger java.math.BigInteger
      StackMap stack:
            iconst_0
            ireturn
         4: .line 125
      StackMap locals:
      StackMap stack:
            aload 3 /* s */
            getstatic org.bouncycastle.crypto.signers.ECDSASigner.ONE:Ljava/math/BigInteger;
            invokevirtual java.math.BigInteger.compareTo:(Ljava/math/BigInteger;)I
            iflt 5
            aload 3 /* s */
            aload 4 /* n */
            invokevirtual java.math.BigInteger.compareTo:(Ljava/math/BigInteger;)I
            iflt 6
         5: .line 127
      StackMap locals:
      StackMap stack:
            iconst_0
            ireturn
         6: .line 130
      StackMap locals:
      StackMap stack:
            aload 3 /* s */
            aload 4 /* n */
            invokevirtual java.math.BigInteger.modInverse:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            astore 6 /* c */
        start local 6 // java.math.BigInteger c
         7: .line 132
            aload 5 /* e */
            aload 6 /* c */
            invokevirtual java.math.BigInteger.multiply:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            aload 4 /* n */
            invokevirtual java.math.BigInteger.mod:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            astore 7 /* u1 */
        start local 7 // java.math.BigInteger u1
         8: .line 133
            aload 2 /* r */
            aload 6 /* c */
            invokevirtual java.math.BigInteger.multiply:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            aload 4 /* n */
            invokevirtual java.math.BigInteger.mod:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            astore 8 /* u2 */
        start local 8 // java.math.BigInteger u2
         9: .line 135
            aload 0 /* this */
            getfield org.bouncycastle.crypto.signers.ECDSASigner.key:Lorg/bouncycastle/crypto/params/ECKeyParameters;
            invokevirtual org.bouncycastle.crypto.params.ECKeyParameters.getParameters:()Lorg/bouncycastle/crypto/params/ECDomainParameters;
            invokevirtual org.bouncycastle.crypto.params.ECDomainParameters.getG:()Lorg/bouncycastle/math/ec/ECPoint;
            astore 9 /* G */
        start local 9 // org.bouncycastle.math.ec.ECPoint G
        10: .line 136
            aload 0 /* this */
            getfield org.bouncycastle.crypto.signers.ECDSASigner.key:Lorg/bouncycastle/crypto/params/ECKeyParameters;
            checkcast org.bouncycastle.crypto.params.ECPublicKeyParameters
            invokevirtual org.bouncycastle.crypto.params.ECPublicKeyParameters.getQ:()Lorg/bouncycastle/math/ec/ECPoint;
            astore 10 /* Q */
        start local 10 // org.bouncycastle.math.ec.ECPoint Q
        11: .line 138
            aload 9 /* G */
            aload 7 /* u1 */
            aload 10 /* Q */
            aload 8 /* u2 */
            invokestatic org.bouncycastle.math.ec.ECAlgorithms.sumOfTwoMultiplies:(Lorg/bouncycastle/math/ec/ECPoint;Ljava/math/BigInteger;Lorg/bouncycastle/math/ec/ECPoint;Ljava/math/BigInteger;)Lorg/bouncycastle/math/ec/ECPoint;
            astore 11 /* point */
        start local 11 // org.bouncycastle.math.ec.ECPoint point
        12: .line 140
            aload 11 /* point */
            invokevirtual org.bouncycastle.math.ec.ECPoint.getX:()Lorg/bouncycastle/math/ec/ECFieldElement;
            invokevirtual org.bouncycastle.math.ec.ECFieldElement.toBigInteger:()Ljava/math/BigInteger;
            aload 4 /* n */
            invokevirtual java.math.BigInteger.mod:(Ljava/math/BigInteger;)Ljava/math/BigInteger;
            astore 12 /* v */
        start local 12 // java.math.BigInteger v
        13: .line 142
            aload 12 /* v */
            aload 2 /* r */
            invokevirtual java.math.BigInteger.equals:(Ljava/lang/Object;)Z
            ireturn
        end local 12 // java.math.BigInteger v
        end local 11 // org.bouncycastle.math.ec.ECPoint point
        end local 10 // org.bouncycastle.math.ec.ECPoint Q
        end local 9 // org.bouncycastle.math.ec.ECPoint G
        end local 8 // java.math.BigInteger u2
        end local 7 // java.math.BigInteger u1
        end local 6 // java.math.BigInteger c
        end local 5 // java.math.BigInteger e
        end local 4 // java.math.BigInteger n
        end local 3 // java.math.BigInteger s
        end local 2 // java.math.BigInteger r
        end local 1 // byte[] message
        end local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
      LocalVariableTable:
        Start  End  Slot     Name  Signature
            0   14     0     this  Lorg/bouncycastle/crypto/signers/ECDSASigner;
            0   14     1  message  [B
            0   14     2        r  Ljava/math/BigInteger;
            0   14     3        s  Ljava/math/BigInteger;
            1   14     4        n  Ljava/math/BigInteger;
            2   14     5        e  Ljava/math/BigInteger;
            7   14     6        c  Ljava/math/BigInteger;
            8   14     7       u1  Ljava/math/BigInteger;
            9   14     8       u2  Ljava/math/BigInteger;
           10   14     9        G  Lorg/bouncycastle/math/ec/ECPoint;
           11   14    10        Q  Lorg/bouncycastle/math/ec/ECPoint;
           12   14    11    point  Lorg/bouncycastle/math/ec/ECPoint;
           13   14    12        v  Ljava/math/BigInteger;
    MethodParameters:
         Name  Flags
      message  
      r        
      s        

  private java.math.BigInteger calculateE(java.math.BigInteger, byte[]);
    descriptor: (Ljava/math/BigInteger;[B)Ljava/math/BigInteger;
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=4, locals=5, args_size=3
        start local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
        start local 1 // java.math.BigInteger n
        start local 2 // byte[] message
         0: .line 147
            aload 1 /* n */
            invokevirtual java.math.BigInteger.bitLength:()I
            aload 2 /* message */
            arraylength
            bipush 8
            imul
            if_icmple 2
         1: .line 149
            new java.math.BigInteger
            dup
            iconst_1
            aload 2 /* message */
            invokespecial java.math.BigInteger.<init>:(I[B)V
            areturn
         2: .line 153
      StackMap locals:
      StackMap stack:
            aload 2 /* message */
            arraylength
            bipush 8
            imul
            istore 3 /* messageBitLength */
        start local 3 // int messageBitLength
         3: .line 154
            new java.math.BigInteger
            dup
            iconst_1
            aload 2 /* message */
            invokespecial java.math.BigInteger.<init>:(I[B)V
            astore 4 /* trunc */
        start local 4 // java.math.BigInteger trunc
         4: .line 156
            iload 3 /* messageBitLength */
            aload 1 /* n */
            invokevirtual java.math.BigInteger.bitLength:()I
            isub
            ifle 6
         5: .line 158
            aload 4 /* trunc */
            iload 3 /* messageBitLength */
            aload 1 /* n */
            invokevirtual java.math.BigInteger.bitLength:()I
            isub
            invokevirtual java.math.BigInteger.shiftRight:(I)Ljava/math/BigInteger;
            astore 4 /* trunc */
         6: .line 161
      StackMap locals: int java.math.BigInteger
      StackMap stack:
            aload 4 /* trunc */
            areturn
        end local 4 // java.math.BigInteger trunc
        end local 3 // int messageBitLength
        end local 2 // byte[] message
        end local 1 // java.math.BigInteger n
        end local 0 // org.bouncycastle.crypto.signers.ECDSASigner this
      LocalVariableTable:
        Start  End  Slot              Name  Signature
            0    7     0              this  Lorg/bouncycastle/crypto/signers/ECDSASigner;
            0    7     1                 n  Ljava/math/BigInteger;
            0    7     2           message  [B
            3    7     3  messageBitLength  I
            4    7     4             trunc  Ljava/math/BigInteger;
    MethodParameters:
         Name  Flags
      n        
      message  
}
SourceFile: "ECDSASigner.java"