using System;
using System.Collections;
using System.Globalization;
using System.IO;

using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.CryptoPro;
using Org.BouncyCastle.Asn1.Nist;
using Org.BouncyCastle.Asn1.Pkcs;
using Org.BouncyCastle.Asn1.TeleTrust;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Asn1.X9;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Crypto.Digests;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Engines;
using Org.BouncyCastle.Crypto.Signers;
using Org.BouncyCastle.Utilities;

namespace Org.BouncyCastle.Security
{
    /// <summary>
    ///  Signer Utility class contains methods that can not be specifically grouped into other classes.
    /// </summary>
    public sealed class SignerUtilities
    {
		private SignerUtilities()
		{
		}

		internal static readonly IDictionary algorithms = Platform.CreateHashtable();
        internal static readonly IDictionary oids = Platform.CreateHashtable();

		static SignerUtilities()
        {
			algorithms["MD2WITHRSA"] = "MD2withRSA";
            algorithms["MD2WITHRSAENCRYPTION"] = "MD2withRSA";
            algorithms[PkcsObjectIdentifiers.MD2WithRsaEncryption.Id] = "MD2withRSA";

            algorithms["MD4WITHRSA"] = "MD4withRSA";
            algorithms["MD4WITHRSAENCRYPTION"] = "MD4withRSA";
            algorithms[PkcsObjectIdentifiers.MD4WithRsaEncryption.Id] = "MD4withRSA";

            algorithms["MD5WITHRSA"] = "MD5withRSA";
            algorithms["MD5WITHRSAENCRYPTION"] = "MD5withRSA";
            algorithms[PkcsObjectIdentifiers.MD5WithRsaEncryption.Id] = "MD5withRSA";

            algorithms["SHA1WITHRSA"] = "SHA-1withRSA";
            algorithms["SHA1WITHRSAENCRYPTION"] = "SHA-1withRSA";
            algorithms[PkcsObjectIdentifiers.Sha1WithRsaEncryption.Id] = "SHA-1withRSA";
            algorithms["SHA-1WITHRSA"] = "SHA-1withRSA";

            algorithms["SHA224WITHRSA"] = "SHA-224withRSA";
            algorithms["SHA224WITHRSAENCRYPTION"] = "SHA-224withRSA";
            algorithms[PkcsObjectIdentifiers.Sha224WithRsaEncryption.Id] = "SHA-224withRSA";
            algorithms["SHA-224WITHRSA"] = "SHA-224withRSA";

            algorithms["SHA256WITHRSA"] = "SHA-256withRSA";
            algorithms["SHA256WITHRSAENCRYPTION"] = "SHA-256withRSA";
            algorithms[PkcsObjectIdentifiers.Sha256WithRsaEncryption.Id] = "SHA-256withRSA";
            algorithms["SHA-256WITHRSA"] = "SHA-256withRSA";

            algorithms["SHA384WITHRSA"] = "SHA-384withRSA";
            algorithms["SHA384WITHRSAENCRYPTION"] = "SHA-384withRSA";
            algorithms[PkcsObjectIdentifiers.Sha384WithRsaEncryption.Id] = "SHA-384withRSA";
            algorithms["SHA-384WITHRSA"] = "SHA-384withRSA";

            algorithms["SHA512WITHRSA"] = "SHA-512withRSA";
            algorithms["SHA512WITHRSAENCRYPTION"] = "SHA-512withRSA";
            algorithms[PkcsObjectIdentifiers.Sha512WithRsaEncryption.Id] = "SHA-512withRSA";
            algorithms["SHA-512WITHRSA"] = "SHA-512withRSA";

			algorithms["PSSWITHRSA"] = "PSSwithRSA";
			algorithms["RSASSA-PSS"] = "PSSwithRSA";
			algorithms[PkcsObjectIdentifiers.IdRsassaPss.Id] = "PSSwithRSA";
			algorithms["RSAPSS"] = "PSSwithRSA";

			algorithms["SHA1WITHRSAANDMGF1"] = "SHA-1withRSAandMGF1";
			algorithms["SHA-1WITHRSAANDMGF1"] = "SHA-1withRSAandMGF1";
			algorithms["SHA1WITHRSA/PSS"] = "SHA-1withRSAandMGF1";
			algorithms["SHA-1WITHRSA/PSS"] = "SHA-1withRSAandMGF1";

			algorithms["SHA224WITHRSAANDMGF1"] = "SHA-224withRSAandMGF1";
			algorithms["SHA-224WITHRSAANDMGF1"] = "SHA-224withRSAandMGF1";
			algorithms["SHA224WITHRSA/PSS"] = "SHA-224withRSAandMGF1";
			algorithms["SHA-224WITHRSA/PSS"] = "SHA-224withRSAandMGF1";

			algorithms["SHA256WITHRSAANDMGF1"] = "SHA-256withRSAandMGF1";
            algorithms["SHA-256WITHRSAANDMGF1"] = "SHA-256withRSAandMGF1";
			algorithms["SHA256WITHRSA/PSS"] = "SHA-256withRSAandMGF1";
			algorithms["SHA-256WITHRSA/PSS"] = "SHA-256withRSAandMGF1";

            algorithms["SHA384WITHRSAANDMGF1"] = "SHA-384withRSAandMGF1";
            algorithms["SHA-384WITHRSAANDMGF1"] = "SHA-384withRSAandMGF1";
			algorithms["SHA384WITHRSA/PSS"] = "SHA-384withRSAandMGF1";
			algorithms["SHA-384WITHRSA/PSS"] = "SHA-384withRSAandMGF1";

            algorithms["SHA512WITHRSAANDMGF1"] = "SHA-512withRSAandMGF1";
            algorithms["SHA-512WITHRSAANDMGF1"] = "SHA-512withRSAandMGF1";
			algorithms["SHA512WITHRSA/PSS"] = "SHA-512withRSAandMGF1";
			algorithms["SHA-512WITHRSA/PSS"] = "SHA-512withRSAandMGF1";

			algorithms["RIPEMD128WITHRSA"] = "RIPEMD128withRSA";
            algorithms["RIPEMD128WITHRSAENCRYPTION"] = "RIPEMD128withRSA";
            algorithms[TeleTrusTObjectIdentifiers.RsaSignatureWithRipeMD128.Id] = "RIPEMD128withRSA";

			algorithms["RIPEMD160WITHRSA"] = "RIPEMD160withRSA";
            algorithms["RIPEMD160WITHRSAENCRYPTION"] = "RIPEMD160withRSA";
            algorithms[TeleTrusTObjectIdentifiers.RsaSignatureWithRipeMD160.Id] = "RIPEMD160withRSA";

            algorithms["RIPEMD256WITHRSA"] = "RIPEMD256withRSA";
            algorithms["RIPEMD256WITHRSAENCRYPTION"] = "RIPEMD256withRSA";
            algorithms[TeleTrusTObjectIdentifiers.RsaSignatureWithRipeMD256.Id] = "RIPEMD256withRSA";

			algorithms["NONEWITHRSA"] = "RSA";
			algorithms["RSAWITHNONE"] = "RSA";
			algorithms["RAWRSA"] = "RSA";

			algorithms["RAWRSAPSS"] = "RAWRSASSA-PSS";
			algorithms["NONEWITHRSAPSS"] = "RAWRSASSA-PSS";
			algorithms["NONEWITHRSASSA-PSS"] = "RAWRSASSA-PSS";

			algorithms["NONEWITHDSA"] = "NONEwithDSA";
			algorithms["DSAWITHNONE"] = "NONEwithDSA";
			algorithms["RAWDSA"] = "NONEwithDSA";

			algorithms["DSA"] = "SHA-1withDSA";
			algorithms["DSAWITHSHA1"] = "SHA-1withDSA";
			algorithms["DSAWITHSHA-1"] = "SHA-1withDSA";
			algorithms["SHA/DSA"] = "SHA-1withDSA";
			algorithms["SHA1/DSA"] = "SHA-1withDSA";
			algorithms["SHA-1/DSA"] = "SHA-1withDSA";
			algorithms["SHA1WITHDSA"] = "SHA-1withDSA";
            algorithms["SHA-1WITHDSA"] = "SHA-1withDSA";
            algorithms[X9ObjectIdentifiers.IdDsaWithSha1.Id] = "SHA-1withDSA";

			algorithms["DSAWITHSHA224"] = "SHA-224withDSA";
			algorithms["DSAWITHSHA-224"] = "SHA-224withDSA";
			algorithms["SHA224/DSA"] = "SHA-224withDSA";
			algorithms["SHA-224/DSA"] = "SHA-224withDSA";
			algorithms["SHA224WITHDSA"] = "SHA-224withDSA";
			algorithms["SHA-224WITHDSA"] = "SHA-224withDSA";
			algorithms[NistObjectIdentifiers.DsaWithSha224.Id] = "SHA-224withDSA";

			algorithms["DSAWITHSHA256"] = "SHA-256withDSA";
			algorithms["DSAWITHSHA-256"] = "SHA-256withDSA";
			algorithms["SHA256/DSA"] = "SHA-256withDSA";
			algorithms["SHA-256/DSA"] = "SHA-256withDSA";
			algorithms["SHA256WITHDSA"] = "SHA-256withDSA";
			algorithms["SHA-256WITHDSA"] = "SHA-256withDSA";
			algorithms[NistObjectIdentifiers.DsaWithSha256.Id] = "SHA-256withDSA";

			algorithms["DSAWITHSHA384"] = "SHA-384withDSA";
			algorithms["DSAWITHSHA-384"] = "SHA-384withDSA";
			algorithms["SHA384/DSA"] = "SHA-384withDSA";
			algorithms["SHA-384/DSA"] = "SHA-384withDSA";
			algorithms["SHA384WITHDSA"] = "SHA-384withDSA";
			algorithms["SHA-384WITHDSA"] = "SHA-384withDSA";
			algorithms[NistObjectIdentifiers.DsaWithSha384.Id] = "SHA-384withDSA";

			algorithms["DSAWITHSHA512"] = "SHA-512withDSA";
			algorithms["DSAWITHSHA-512"] = "SHA-512withDSA";
			algorithms["SHA512/DSA"] = "SHA-512withDSA";
			algorithms["SHA-512/DSA"] = "SHA-512withDSA";
			algorithms["SHA512WITHDSA"] = "SHA-512withDSA";
			algorithms["SHA-512WITHDSA"] = "SHA-512withDSA";
			algorithms[NistObjectIdentifiers.DsaWithSha512.Id] = "SHA-512withDSA";

			algorithms["NONEWITHECDSA"] = "NONEwithECDSA";
			algorithms["ECDSAWITHNONE"] = "NONEwithECDSA";

			algorithms["ECDSA"] = "SHA-1withECDSA";
			algorithms["SHA1/ECDSA"] = "SHA-1withECDSA";
			algorithms["SHA-1/ECDSA"] = "SHA-1withECDSA";
			algorithms["ECDSAWITHSHA1"] = "SHA-1withECDSA";
			algorithms["ECDSAWITHSHA-1"] = "SHA-1withECDSA";
			algorithms["SHA1WITHECDSA"] = "SHA-1withECDSA";
            algorithms["SHA-1WITHECDSA"] = "SHA-1withECDSA";
			algorithms[X9ObjectIdentifiers.ECDsaWithSha1.Id] = "SHA-1withECDSA";
			algorithms[TeleTrusTObjectIdentifiers.ECSignWithSha1.Id] = "SHA-1withECDSA";

			algorithms["SHA224/ECDSA"] = "SHA-224withECDSA";
			algorithms["SHA-224/ECDSA"] = "SHA-224withECDSA";
			algorithms["ECDSAWITHSHA224"] = "SHA-224withECDSA";
			algorithms["ECDSAWITHSHA-224"] = "SHA-224withECDSA";
			algorithms["SHA224WITHECDSA"] = "SHA-224withECDSA";
			algorithms["SHA-224WITHECDSA"] = "SHA-224withECDSA";
			algorithms[X9ObjectIdentifiers.ECDsaWithSha224.Id] = "SHA-224withECDSA";

			algorithms["SHA256/ECDSA"] = "SHA-256withECDSA";
			algorithms["SHA-256/ECDSA"] = "SHA-256withECDSA";
			algorithms["ECDSAWITHSHA256"] = "SHA-256withECDSA";
			algorithms["ECDSAWITHSHA-256"] = "SHA-256withECDSA";
			algorithms["SHA256WITHECDSA"] = "SHA-256withECDSA";
			algorithms["SHA-256WITHECDSA"] = "SHA-256withECDSA";
			algorithms[X9ObjectIdentifiers.ECDsaWithSha256.Id] = "SHA-256withECDSA";

			algorithms["SHA384/ECDSA"] = "SHA-384withECDSA";
			algorithms["SHA-384/ECDSA"] = "SHA-384withECDSA";
			algorithms["ECDSAWITHSHA384"] = "SHA-384withECDSA";
			algorithms["ECDSAWITHSHA-384"] = "SHA-384withECDSA";
			algorithms["SHA384WITHECDSA"] = "SHA-384withECDSA";
			algorithms["SHA-384WITHECDSA"] = "SHA-384withECDSA";
			algorithms[X9ObjectIdentifiers.ECDsaWithSha384.Id] = "SHA-384withECDSA";

			algorithms["SHA512/ECDSA"] = "SHA-512withECDSA";
			algorithms["SHA-512/ECDSA"] = "SHA-512withECDSA";
			algorithms["ECDSAWITHSHA512"] = "SHA-512withECDSA";
			algorithms["ECDSAWITHSHA-512"] = "SHA-512withECDSA";
			algorithms["SHA512WITHECDSA"] = "SHA-512withECDSA";
			algorithms["SHA-512WITHECDSA"] = "SHA-512withECDSA";
			algorithms[X9ObjectIdentifiers.ECDsaWithSha512.Id] = "SHA-512withECDSA";

			algorithms["RIPEMD160/ECDSA"] = "RIPEMD160withECDSA";
			algorithms["SHA-512/ECDSA"] = "RIPEMD160withECDSA";
			algorithms["ECDSAWITHRIPEMD160"] = "RIPEMD160withECDSA";
			algorithms["ECDSAWITHRIPEMD160"] = "RIPEMD160withECDSA";
			algorithms["RIPEMD160WITHECDSA"] = "RIPEMD160withECDSA";
			algorithms["RIPEMD160WITHECDSA"] = "RIPEMD160withECDSA";
			algorithms[TeleTrusTObjectIdentifiers.ECSignWithRipeMD160.Id] = "RIPEMD160withECDSA";

			algorithms["GOST-3410"] = "GOST3410";
			algorithms["GOST-3410-94"] = "GOST3410";
			algorithms["GOST3411WITHGOST3410"] = "GOST3410";
			algorithms[CryptoProObjectIdentifiers.GostR3411x94WithGostR3410x94.Id] = "GOST3410";

			algorithms["ECGOST-3410"] = "ECGOST3410";
			algorithms["ECGOST-3410-2001"] = "ECGOST3410";
			algorithms["GOST3411WITHECGOST3410"] = "ECGOST3410";
			algorithms[CryptoProObjectIdentifiers.GostR3411x94WithGostR3410x2001.Id] = "ECGOST3410";



			oids["MD2withRSA"] = PkcsObjectIdentifiers.MD2WithRsaEncryption;
            oids["MD4withRSA"] = PkcsObjectIdentifiers.MD4WithRsaEncryption;
            oids["MD5withRSA"] = PkcsObjectIdentifiers.MD5WithRsaEncryption;

            oids["SHA-1withRSA"] = PkcsObjectIdentifiers.Sha1WithRsaEncryption;
            oids["SHA-224withRSA"] = PkcsObjectIdentifiers.Sha224WithRsaEncryption;
            oids["SHA-256withRSA"] = PkcsObjectIdentifiers.Sha256WithRsaEncryption;
            oids["SHA-384withRSA"] = PkcsObjectIdentifiers.Sha384WithRsaEncryption;
            oids["SHA-512withRSA"] = PkcsObjectIdentifiers.Sha512WithRsaEncryption;

			oids["PSSwithRSA"] = PkcsObjectIdentifiers.IdRsassaPss;
			oids["SHA-1withRSAandMGF1"] = PkcsObjectIdentifiers.IdRsassaPss;
			oids["SHA-224withRSAandMGF1"] = PkcsObjectIdentifiers.IdRsassaPss;
			oids["SHA-256withRSAandMGF1"] = PkcsObjectIdentifiers.IdRsassaPss;
			oids["SHA-384withRSAandMGF1"] = PkcsObjectIdentifiers.IdRsassaPss;
			oids["SHA-512withRSAandMGF1"] = PkcsObjectIdentifiers.IdRsassaPss;

			oids["RIPEMD128withRSA"] = TeleTrusTObjectIdentifiers.RsaSignatureWithRipeMD128;
			oids["RIPEMD160withRSA"] = TeleTrusTObjectIdentifiers.RsaSignatureWithRipeMD160;
			oids["RIPEMD256withRSA"] = TeleTrusTObjectIdentifiers.RsaSignatureWithRipeMD256;

			oids["SHA-1withDSA"] = X9ObjectIdentifiers.IdDsaWithSha1;

			oids["SHA-1withECDSA"] = X9ObjectIdentifiers.ECDsaWithSha1;
			oids["SHA-224withECDSA"] = X9ObjectIdentifiers.ECDsaWithSha224;
			oids["SHA-256withECDSA"] = X9ObjectIdentifiers.ECDsaWithSha256;
			oids["SHA-384withECDSA"] = X9ObjectIdentifiers.ECDsaWithSha384;
			oids["SHA-512withECDSA"] = X9ObjectIdentifiers.ECDsaWithSha512;

			oids["GOST3410"] = CryptoProObjectIdentifiers.GostR3411x94WithGostR3410x94;
			oids["ECGOST3410"] = CryptoProObjectIdentifiers.GostR3411x94WithGostR3410x2001;
		}

		/// <summary>
        /// Returns a ObjectIdentifier for a give encoding.
        /// </summary>
        /// <param name="mechanism">A string representation of the encoding.</param>
        /// <returns>A DerObjectIdentifier, null if the Oid is not available.</returns>
		// TODO Don't really want to support this
        public static DerObjectIdentifier GetObjectIdentifier(
			string mechanism)
        {
			if (mechanism == null)
				throw new ArgumentNullException("mechanism");

			mechanism = mechanism.ToUpper(CultureInfo.InvariantCulture);
			string aliased = (string) algorithms[mechanism];

			if (aliased != null)
				mechanism = aliased;

			return (DerObjectIdentifier) oids[mechanism];
		}

		public static ICollection Algorithms
        {
            get { return oids.Keys; }
        }

		public static Asn1Encodable GetDefaultX509Parameters(
			DerObjectIdentifier id)
		{
			return GetDefaultX509Parameters(id.Id);
		}

		public static Asn1Encodable GetDefaultX509Parameters(
			string algorithm)
		{
			if (algorithm == null)
				throw new ArgumentNullException("algorithm");

			algorithm = algorithm.ToUpper(CultureInfo.InvariantCulture);

			string mechanism = (string) algorithms[algorithm];

			if (mechanism == null)
				mechanism = algorithm;

			if (mechanism == "PSSwithRSA")
			{
				// TODO The Sha1Digest here is a default. In JCE version, the actual digest
				// to be used can be overridden by subsequent parameter settings.
				return GetPssX509Parameters("SHA-1");
			}

			if (mechanism.EndsWith("withRSAandMGF1"))
			{
				string digestName = mechanism.Substring(0, mechanism.Length - "withRSAandMGF1".Length);
				return GetPssX509Parameters(digestName);
			}

			return DerNull.Instance;
		}

		private static Asn1Encodable GetPssX509Parameters(
			string	digestName)
		{
			AlgorithmIdentifier hashAlgorithm = new AlgorithmIdentifier(
				DigestUtilities.GetObjectIdentifier(digestName), DerNull.Instance);

			// TODO Is it possible for the MGF hash alg to be different from the PSS one?
			AlgorithmIdentifier maskGenAlgorithm = new AlgorithmIdentifier(
				PkcsObjectIdentifiers.IdMgf1, hashAlgorithm);

			int saltLen = DigestUtilities.GetDigest(digestName).GetDigestSize();
			return new RsassaPssParameters(hashAlgorithm, maskGenAlgorithm,
				new DerInteger(saltLen), new DerInteger(1));
		}

		public static ISigner GetSigner(
			DerObjectIdentifier id)
        {
            return GetSigner(id.Id);
        }

		public static ISigner GetSigner(
			string algorithm)
        {
			if (algorithm == null)
				throw new ArgumentNullException("algorithm");

			algorithm = algorithm.ToUpper(CultureInfo.InvariantCulture);

			string mechanism = (string) algorithms[algorithm];

			if (mechanism == null)
				mechanism = algorithm;

			if (mechanism.Equals("RSA"))
			{
				return (new RsaDigestSigner(new NullDigest()));
			}
			if (mechanism.Equals("MD2withRSA"))
            {
                return (new RsaDigestSigner(new MD2Digest()));
            }
            if (mechanism.Equals("MD4withRSA"))
            {
                return (new RsaDigestSigner(new MD4Digest()));
            }
            if (mechanism.Equals("MD5withRSA"))
            {
                return (new RsaDigestSigner(new MD5Digest()));
            }
            if (mechanism.Equals("SHA-1withRSA"))
            {
                return (new RsaDigestSigner(new Sha1Digest()));
            }
            if (mechanism.Equals("SHA-224withRSA"))
            {
                return (new RsaDigestSigner(new Sha224Digest()));
            }
            if (mechanism.Equals("SHA-256withRSA"))
            {
                return (new RsaDigestSigner(new Sha256Digest()));
            }
            if (mechanism.Equals("SHA-384withRSA"))
            {
                return (new RsaDigestSigner(new Sha384Digest()));
            }
            if (mechanism.Equals("SHA-512withRSA"))
            {
                return (new RsaDigestSigner(new Sha512Digest()));
            }
			if (mechanism.Equals("RIPEMD128withRSA"))
            {
                return (new RsaDigestSigner(new RipeMD128Digest()));
            }
            if (mechanism.Equals("RIPEMD160withRSA"))
            {
                return (new RsaDigestSigner(new RipeMD160Digest()));
            }
            if (mechanism.Equals("RIPEMD256withRSA"))
            {
                return (new RsaDigestSigner(new RipeMD256Digest()));
            }

			if (mechanism.Equals("RAWRSASSA-PSS"))
			{
				// TODO Add support for other parameter settings
				return PssSigner.CreateRawSigner(new RsaBlindedEngine(), new Sha1Digest());
			}
			if (mechanism.Equals("PSSwithRSA"))
			{
				// TODO The Sha1Digest here is a default. In JCE version, the actual digest
				// to be used can be overridden by subsequent parameter settings.
				return (new PssSigner(new RsaBlindedEngine(), new Sha1Digest()));
			}
			if (mechanism.Equals("SHA-1withRSAandMGF1"))
			{
				return (new PssSigner(new RsaBlindedEngine(), new Sha1Digest()));
			}
			if (mechanism.Equals("SHA-224withRSAandMGF1"))
			{
				return (new PssSigner(new RsaBlindedEngine(), new Sha224Digest()));
			}
			if (mechanism.Equals("SHA-256withRSAandMGF1"))
			{
				return (new PssSigner(new RsaBlindedEngine(), new Sha256Digest()));
			}
			if (mechanism.Equals("SHA-384withRSAandMGF1"))
			{
				return (new PssSigner(new RsaBlindedEngine(), new Sha384Digest()));
			}
			if (mechanism.Equals("SHA-512withRSAandMGF1"))
			{
				return (new PssSigner(new RsaBlindedEngine(), new Sha512Digest()));
			}

			if (mechanism.Equals("NONEwithDSA"))
			{
				return (new DsaDigestSigner(new DsaSigner(), new NullDigest()));
			}
			if (mechanism.Equals("SHA-1withDSA"))
            {
                return (new DsaDigestSigner(new DsaSigner(), new Sha1Digest()));
            }
			if (mechanism.Equals("SHA-224withDSA"))
			{
				return (new DsaDigestSigner(new DsaSigner(), new Sha224Digest()));
			}
			if (mechanism.Equals("SHA-256withDSA"))
			{
				return (new DsaDigestSigner(new DsaSigner(), new Sha256Digest()));
			}
			if (mechanism.Equals("SHA-384withDSA"))
			{
				return (new DsaDigestSigner(new DsaSigner(), new Sha384Digest()));
			}
			if (mechanism.Equals("SHA-512withDSA"))
			{
				return (new DsaDigestSigner(new DsaSigner(), new Sha512Digest()));
			}

			if (mechanism.Equals("NONEwithECDSA"))
			{
				return (new DsaDigestSigner(new ECDsaSigner(), new NullDigest()));
			}
			if (mechanism.Equals("SHA-1withECDSA"))
            {
                return (new DsaDigestSigner(new ECDsaSigner(), new Sha1Digest()));
            }
			if (mechanism.Equals("SHA-224withECDSA"))
			{
				return (new DsaDigestSigner(new ECDsaSigner(), new Sha224Digest()));
			}
			if (mechanism.Equals("SHA-256withECDSA"))
			{
				return (new DsaDigestSigner(new ECDsaSigner(), new Sha256Digest()));
			}
			if (mechanism.Equals("SHA-384withECDSA"))
			{
				return (new DsaDigestSigner(new ECDsaSigner(), new Sha384Digest()));
			}
			if (mechanism.Equals("SHA-512withECDSA"))
			{
				return (new DsaDigestSigner(new ECDsaSigner(), new Sha512Digest()));
			}

			if (mechanism.Equals("RIPEMD160withECDSA"))
			{
				return (new DsaDigestSigner(new ECDsaSigner(), new RipeMD160Digest()));
			}

			if (mechanism.Equals("SHA1WITHECNR"))
			{
				return (new DsaDigestSigner(new ECNRSigner(), new Sha1Digest()));
			}
			if (mechanism.Equals("SHA224WITHECNR"))
			{
				return (new DsaDigestSigner(new ECNRSigner(), new Sha224Digest()));
			}
			if (mechanism.Equals("SHA256WITHECNR"))
			{
				return (new DsaDigestSigner(new ECNRSigner(), new Sha256Digest()));
			}
			if (mechanism.Equals("SHA384WITHECNR"))
			{
				return (new DsaDigestSigner(new ECNRSigner(), new Sha384Digest()));
			}
			if (mechanism.Equals("SHA512WITHECNR"))
			{
				return (new DsaDigestSigner(new ECNRSigner(), new Sha512Digest()));
			}

			if (mechanism.Equals("GOST3410"))
			{
				return new Gost3410DigestSigner(new Gost3410Signer(), new Gost3411Digest());
			}
			if (mechanism.Equals("ECGOST3410"))
			{
				return new Gost3410DigestSigner(new ECGost3410Signer(), new Gost3411Digest());
			}

			if (mechanism.Equals("SHA1WITHRSA/ISO9796-2"))
			{
				return new Iso9796d2Signer(new RsaBlindedEngine(), new Sha1Digest(), true);
			}
			if (mechanism.Equals("MD5WITHRSA/ISO9796-2"))
			{
				return new Iso9796d2Signer(new RsaBlindedEngine(), new MD5Digest(), true);
			}
			if (mechanism.Equals("RIPEMD160WITHRSA/ISO9796-2"))
			{
				return new Iso9796d2Signer(new RsaBlindedEngine(), new RipeMD160Digest(), true);
			}

			throw new SecurityUtilityException("Signer " + algorithm + " not recognised.");
        }

        public static string GetEncodingName(
			DerObjectIdentifier oid)
        {
            return (string) algorithms[oid.Id];
        }
    }
}
