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. 
class org.bouncycastle.jce.provider.X509SignatureUtil
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: org.bouncycastle.jce.provider.X509SignatureUtil
  super_class: java.lang.Object
{
  private static final org.bouncycastle.asn1.ASN1Null derNull;
    descriptor: Lorg/bouncycastle/asn1/ASN1Null;
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL

  static void <clinit>();
    descriptor: ()V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=2, locals=0, args_size=0
         0: .line 28
            new org.bouncycastle.asn1.DERNull
            dup
            invokespecial org.bouncycastle.asn1.DERNull.<init>:()V
            putstatic org.bouncycastle.jce.provider.X509SignatureUtil.derNull:Lorg/bouncycastle/asn1/ASN1Null;
            return
      LocalVariableTable:
        Start  End  Slot  Name  Signature

  void <init>();
    descriptor: ()V
    flags: (0x0000) 
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.bouncycastle.jce.provider.X509SignatureUtil this
         0: .line 26
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // org.bouncycastle.jce.provider.X509SignatureUtil this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/bouncycastle/jce/provider/X509SignatureUtil;

  static void setSignatureParameters(java.security.Signature, org.bouncycastle.asn1.DEREncodable);
    descriptor: (Ljava/security/Signature;Lorg/bouncycastle/asn1/DEREncodable;)V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=5, locals=4, args_size=2
        start local 0 // java.security.Signature signature
        start local 1 // org.bouncycastle.asn1.DEREncodable params
         0: .line 35
            aload 1 /* params */
            ifnull 11
            getstatic org.bouncycastle.jce.provider.X509SignatureUtil.derNull:Lorg/bouncycastle/asn1/ASN1Null;
            aload 1 /* params */
            invokevirtual org.bouncycastle.asn1.ASN1Null.equals:(Ljava/lang/Object;)Z
            ifne 11
         1: .line 37
            aload 0 /* signature */
            invokevirtual java.security.Signature.getAlgorithm:()Ljava/lang/String;
            aload 0 /* signature */
            invokevirtual java.security.Signature.getProvider:()Ljava/security/Provider;
            invokestatic java.security.AlgorithmParameters.getInstance:(Ljava/lang/String;Ljava/security/Provider;)Ljava/security/AlgorithmParameters;
            astore 2 /* sigParams */
        start local 2 // java.security.AlgorithmParameters sigParams
         2: .line 41
            aload 2 /* sigParams */
            aload 1 /* params */
            invokeinterface org.bouncycastle.asn1.DEREncodable.getDERObject:()Lorg/bouncycastle/asn1/DERObject;
            invokevirtual org.bouncycastle.asn1.DERObject.getDEREncoded:()[B
            invokevirtual java.security.AlgorithmParameters.init:([B)V
         3: .line 42
            goto 6
         4: .line 43
      StackMap locals: java.security.Signature org.bouncycastle.asn1.DEREncodable java.security.AlgorithmParameters
      StackMap stack: java.io.IOException
            astore 3 /* e */
        start local 3 // java.io.IOException e
         5: .line 45
            new java.security.SignatureException
            dup
            new java.lang.StringBuilder
            dup
            ldc "IOException decoding parameters: "
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            aload 3 /* e */
            invokevirtual java.io.IOException.getMessage:()Ljava/lang/String;
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            invokespecial java.security.SignatureException.<init>:(Ljava/lang/String;)V
            athrow
        end local 3 // java.io.IOException e
         6: .line 48
      StackMap locals:
      StackMap stack:
            aload 0 /* signature */
            invokevirtual java.security.Signature.getAlgorithm:()Ljava/lang/String;
            ldc "MGF1"
            invokevirtual java.lang.String.endsWith:(Ljava/lang/String;)Z
            ifeq 11
         7: .line 52
            aload 0 /* signature */
            aload 2 /* sigParams */
            ldc Ljava/security/spec/PSSParameterSpec;
            invokevirtual java.security.AlgorithmParameters.getParameterSpec:(Ljava/lang/Class;)Ljava/security/spec/AlgorithmParameterSpec;
            invokevirtual java.security.Signature.setParameter:(Ljava/security/spec/AlgorithmParameterSpec;)V
         8: .line 53
            goto 11
         9: .line 54
      StackMap locals:
      StackMap stack: java.security.GeneralSecurityException
            astore 3 /* e */
        start local 3 // java.security.GeneralSecurityException e
        10: .line 56
            new java.security.SignatureException
            dup
            new java.lang.StringBuilder
            dup
            ldc "Exception extracting parameters: "
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            aload 3 /* e */
            invokevirtual java.security.GeneralSecurityException.getMessage:()Ljava/lang/String;
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            invokespecial java.security.SignatureException.<init>:(Ljava/lang/String;)V
            athrow
        end local 3 // java.security.GeneralSecurityException e
        end local 2 // java.security.AlgorithmParameters sigParams
        11: .line 60
      StackMap locals:
      StackMap stack:
            return
        end local 1 // org.bouncycastle.asn1.DEREncodable params
        end local 0 // java.security.Signature signature
      LocalVariableTable:
        Start  End  Slot       Name  Signature
            0   12     0  signature  Ljava/security/Signature;
            0   12     1     params  Lorg/bouncycastle/asn1/DEREncodable;
            2   11     2  sigParams  Ljava/security/AlgorithmParameters;
            5    6     3          e  Ljava/io/IOException;
           10   11     3          e  Ljava/security/GeneralSecurityException;
      Exception table:
        from    to  target  type
           2     3       4  Class java.io.IOException
           7     8       9  Class java.security.GeneralSecurityException
    Exceptions:
      throws java.security.NoSuchAlgorithmException, java.security.SignatureException, java.security.InvalidKeyException
    MethodParameters:
           Name  Flags
      signature  
      params     

  static java.lang.String getSignatureName(org.bouncycastle.asn1.x509.AlgorithmIdentifier);
    descriptor: (Lorg/bouncycastle/asn1/x509/AlgorithmIdentifier;)Ljava/lang/String;
    flags: (0x0008) ACC_STATIC
    Code:
      stack=4, locals=3, args_size=1
        start local 0 // org.bouncycastle.asn1.x509.AlgorithmIdentifier sigAlgId
         0: .line 65
            aload 0 /* sigAlgId */
            invokevirtual org.bouncycastle.asn1.x509.AlgorithmIdentifier.getParameters:()Lorg/bouncycastle/asn1/DEREncodable;
            astore 1 /* params */
        start local 1 // org.bouncycastle.asn1.DEREncodable params
         1: .line 67
            aload 1 /* params */
            ifnull 8
            getstatic org.bouncycastle.jce.provider.X509SignatureUtil.derNull:Lorg/bouncycastle/asn1/ASN1Null;
            aload 1 /* params */
            invokevirtual org.bouncycastle.asn1.ASN1Null.equals:(Ljava/lang/Object;)Z
            ifne 8
         2: .line 69
            aload 0 /* sigAlgId */
            invokevirtual org.bouncycastle.asn1.x509.AlgorithmIdentifier.getObjectId:()Lorg/bouncycastle/asn1/DERObjectIdentifier;
            getstatic org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers.id_RSASSA_PSS:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            invokevirtual org.bouncycastle.asn1.DERObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 5
         3: .line 71
            aload 1 /* params */
            invokestatic org.bouncycastle.asn1.pkcs.RSASSAPSSparams.getInstance:(Ljava/lang/Object;)Lorg/bouncycastle/asn1/pkcs/RSASSAPSSparams;
            astore 2 /* rsaParams */
        start local 2 // org.bouncycastle.asn1.pkcs.RSASSAPSSparams rsaParams
         4: .line 73
            new java.lang.StringBuilder
            dup
            aload 2 /* rsaParams */
            invokevirtual org.bouncycastle.asn1.pkcs.RSASSAPSSparams.getHashAlgorithm:()Lorg/bouncycastle/asn1/x509/AlgorithmIdentifier;
            invokevirtual org.bouncycastle.asn1.x509.AlgorithmIdentifier.getObjectId:()Lorg/bouncycastle/asn1/DERObjectIdentifier;
            invokestatic org.bouncycastle.jce.provider.X509SignatureUtil.getDigestAlgName:(Lorg/bouncycastle/asn1/DERObjectIdentifier;)Ljava/lang/String;
            invokestatic java.lang.String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            ldc "withRSAandMGF1"
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            areturn
        end local 2 // org.bouncycastle.asn1.pkcs.RSASSAPSSparams rsaParams
         5: .line 75
      StackMap locals: org.bouncycastle.asn1.DEREncodable
      StackMap stack:
            aload 0 /* sigAlgId */
            invokevirtual org.bouncycastle.asn1.x509.AlgorithmIdentifier.getObjectId:()Lorg/bouncycastle/asn1/DERObjectIdentifier;
            getstatic org.bouncycastle.asn1.x9.X9ObjectIdentifiers.ecdsa_with_SHA2:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            invokevirtual org.bouncycastle.asn1.DERObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 8
         6: .line 77
            aload 1 /* params */
            invokestatic org.bouncycastle.asn1.ASN1Sequence.getInstance:(Ljava/lang/Object;)Lorg/bouncycastle/asn1/ASN1Sequence;
            astore 2 /* ecDsaParams */
        start local 2 // org.bouncycastle.asn1.ASN1Sequence ecDsaParams
         7: .line 79
            new java.lang.StringBuilder
            dup
            aload 2 /* ecDsaParams */
            iconst_0
            invokevirtual org.bouncycastle.asn1.ASN1Sequence.getObjectAt:(I)Lorg/bouncycastle/asn1/DEREncodable;
            checkcast org.bouncycastle.asn1.DERObjectIdentifier
            invokestatic org.bouncycastle.jce.provider.X509SignatureUtil.getDigestAlgName:(Lorg/bouncycastle/asn1/DERObjectIdentifier;)Ljava/lang/String;
            invokestatic java.lang.String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            ldc "withECDSA"
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            areturn
        end local 2 // org.bouncycastle.asn1.ASN1Sequence ecDsaParams
         8: .line 83
      StackMap locals:
      StackMap stack:
            aload 0 /* sigAlgId */
            invokevirtual org.bouncycastle.asn1.x509.AlgorithmIdentifier.getObjectId:()Lorg/bouncycastle/asn1/DERObjectIdentifier;
            invokevirtual org.bouncycastle.asn1.DERObjectIdentifier.getId:()Ljava/lang/String;
            areturn
        end local 1 // org.bouncycastle.asn1.DEREncodable params
        end local 0 // org.bouncycastle.asn1.x509.AlgorithmIdentifier sigAlgId
      LocalVariableTable:
        Start  End  Slot         Name  Signature
            0    9     0     sigAlgId  Lorg/bouncycastle/asn1/x509/AlgorithmIdentifier;
            1    9     1       params  Lorg/bouncycastle/asn1/DEREncodable;
            4    5     2    rsaParams  Lorg/bouncycastle/asn1/pkcs/RSASSAPSSparams;
            7    8     2  ecDsaParams  Lorg/bouncycastle/asn1/ASN1Sequence;
    MethodParameters:
          Name  Flags
      sigAlgId  

  private static java.lang.String getDigestAlgName(org.bouncycastle.asn1.DERObjectIdentifier);
    descriptor: (Lorg/bouncycastle/asn1/DERObjectIdentifier;)Ljava/lang/String;
    flags: (0x000a) ACC_PRIVATE, ACC_STATIC
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // org.bouncycastle.asn1.DERObjectIdentifier digestAlgOID
         0: .line 93
            getstatic org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers.md5:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.ASN1ObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 2
         1: .line 95
            ldc "MD5"
            areturn
         2: .line 97
      StackMap locals:
      StackMap stack:
            getstatic org.bouncycastle.asn1.oiw.OIWObjectIdentifiers.idSHA1:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.ASN1ObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 4
         3: .line 99
            ldc "SHA1"
            areturn
         4: .line 101
      StackMap locals:
      StackMap stack:
            getstatic org.bouncycastle.asn1.nist.NISTObjectIdentifiers.id_sha224:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.ASN1ObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 6
         5: .line 103
            ldc "SHA224"
            areturn
         6: .line 105
      StackMap locals:
      StackMap stack:
            getstatic org.bouncycastle.asn1.nist.NISTObjectIdentifiers.id_sha256:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.ASN1ObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 8
         7: .line 107
            ldc "SHA256"
            areturn
         8: .line 109
      StackMap locals:
      StackMap stack:
            getstatic org.bouncycastle.asn1.nist.NISTObjectIdentifiers.id_sha384:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.ASN1ObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 10
         9: .line 111
            ldc "SHA384"
            areturn
        10: .line 113
      StackMap locals:
      StackMap stack:
            getstatic org.bouncycastle.asn1.nist.NISTObjectIdentifiers.id_sha512:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.ASN1ObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 12
        11: .line 115
            ldc "SHA512"
            areturn
        12: .line 117
      StackMap locals:
      StackMap stack:
            getstatic org.bouncycastle.asn1.teletrust.TeleTrusTObjectIdentifiers.ripemd128:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.ASN1ObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 14
        13: .line 119
            ldc "RIPEMD128"
            areturn
        14: .line 121
      StackMap locals:
      StackMap stack:
            getstatic org.bouncycastle.asn1.teletrust.TeleTrusTObjectIdentifiers.ripemd160:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.ASN1ObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 16
        15: .line 123
            ldc "RIPEMD160"
            areturn
        16: .line 125
      StackMap locals:
      StackMap stack:
            getstatic org.bouncycastle.asn1.teletrust.TeleTrusTObjectIdentifiers.ripemd256:Lorg/bouncycastle/asn1/ASN1ObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.ASN1ObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 18
        17: .line 127
            ldc "RIPEMD256"
            areturn
        18: .line 129
      StackMap locals:
      StackMap stack:
            getstatic org.bouncycastle.asn1.cryptopro.CryptoProObjectIdentifiers.gostR3411:Lorg/bouncycastle/asn1/DERObjectIdentifier;
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.DERObjectIdentifier.equals:(Ljava/lang/Object;)Z
            ifeq 20
        19: .line 131
            ldc "GOST3411"
            areturn
        20: .line 135
      StackMap locals:
      StackMap stack:
            aload 0 /* digestAlgOID */
            invokevirtual org.bouncycastle.asn1.DERObjectIdentifier.getId:()Ljava/lang/String;
            areturn
        end local 0 // org.bouncycastle.asn1.DERObjectIdentifier digestAlgOID
      LocalVariableTable:
        Start  End  Slot          Name  Signature
            0   21     0  digestAlgOID  Lorg/bouncycastle/asn1/DERObjectIdentifier;
    MethodParameters:
              Name  Flags
      digestAlgOID  
}
SourceFile: "X509SignatureUtil.java"