sshd-core/src/main/java/org/apache/sshd/common/cipher/ECCurves.java - mina-sshd - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements. See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership. The ASF licenses this file
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License. You may obtain a copy of the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing,
  * software distributed under the License is distributed on an
  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  * KIND, either express or implied. See the License for the
  * specific language governing permissions and limitations
  * under the License.
  */
 package org.apache.sshd.common.cipher;

 import java.math.BigInteger;
 import java.security.spec.ECField;
 import java.security.spec.ECFieldFp;
 import java.security.spec.ECParameterSpec;
 import java.security.spec.ECPoint;
 import java.security.spec.EllipticCurve;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Set;
 import java.util.TreeSet;

 import org.apache.sshd.common.NamedResource;
 import org.apache.sshd.common.OptionalFeature;
 import org.apache.sshd.common.digest.BuiltinDigests;
 import org.apache.sshd.common.digest.Digest;
 import org.apache.sshd.common.digest.DigestFactory;
 import org.apache.sshd.common.util.GenericUtils;
 import org.apache.sshd.common.util.SecurityUtils;
 import org.apache.sshd.common.util.ValidateUtils;

 /**
  * Utilities for working with elliptic curves.
  *
  * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
  */
 public enum ECCurves implements NamedResource, OptionalFeature {
     nistp256(Constants.NISTP256,
             new ECParameterSpec(
                     new EllipticCurve(
                             new ECFieldFp(new BigInteger("FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF", 16)),
                             new BigInteger("FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFC", 16),
                             new BigInteger("5ac635d8aa3a93e7b3ebbd55769886bc651d06b0cc53b0f63bce3c3e27d2604b", 16)),
                     new ECPoint(
                             new BigInteger("6B17D1F2E12C4247F8BCE6E563A440F277037D812DEB33A0F4A13945D898C296", 16),
                             new BigInteger("4FE342E2FE1A7F9B8EE7EB4A7C0F9E162BCE33576B315ECECBB6406837BF51F5", 16)),
                     new BigInteger("FFFFFFFF00000000FFFFFFFFFFFFFFFFBCE6FAADA7179E84F3B9CAC2FC632551", 16),
                     1),
             32,
             BuiltinDigests.sha256),
     nistp384(Constants.NISTP384,
             new ECParameterSpec(
                     new EllipticCurve(
                             new ECFieldFp(new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFFFF0000000000000000FFFFFFFF", 16)),
                             new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFFFF0000000000000000FFFFFFFC", 16),
                             new BigInteger("B3312FA7E23EE7E4988E056BE3F82D19181D9C6EFE8141120314088F5013875AC656398D8A2ED19D2A85C8EDD3EC2AEF", 16)),
                     new ECPoint(
                             new BigInteger("AA87CA22BE8B05378EB1C71EF320AD746E1D3B628BA79B9859F741E082542A385502F25DBF55296C3A545E3872760AB7", 16),
                             new BigInteger("3617DE4A96262C6F5D9E98BF9292DC29F8F41DBD289A147CE9DA3113B5F0B8C00A60B1CE1D7E819D7A431D7C90EA0E5F", 16)),
                     new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFC7634D81F4372DDF581A0DB248B0A77AECEC196ACCC52973", 16),
                     1),
             48,
             BuiltinDigests.sha384),
     nistp521(Constants.NISTP521,
             new ECParameterSpec(
                     new EllipticCurve(
                             new ECFieldFp(new BigInteger("01FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"
                                                           + "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF", 16)),
                             new BigInteger("01FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"
                                                 + "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFC", 16),
                             new BigInteger("0051953EB9618E1C9A1F929A21A0B68540EEA2DA725B99B315F3B8B489918EF109E156193951"
                                             + "EC7E937B1652C0BD3BB1BF073573DF883D2C34F1EF451FD46B503F00", 16)),
                     new ECPoint(
                             new BigInteger("00C6858E06B70404E9CD9E3ECB662395B4429C648139053FB521F828AF606B4D3DBAA14B5E77"
                                             + "EFE75928FE1DC127A2FFA8DE3348B3C1856A429BF97E7E31C2E5BD66", 16),
                             new BigInteger("011839296A789A3BC0045C8A5FB42C7D1BD998F54449579B446817AFBD17273E662C97EE7299"
                                             + "5EF42640C550B9013FAD0761353C7086A272C24088BE94769FD16650", 16)),
                     new BigInteger("01FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFA51868783BF2F966B"
                                     + "7FCC0148F709A5D03BB5C9B8899C47AEBB6FB71E91386409", 16),
                     1),
             66,
             BuiltinDigests.sha512);

     /**
      * A {@link Set} of all the known curves
      */
     public static final Set<ECCurves> VALUES =
             Collections.unmodifiableSet(EnumSet.allOf(ECCurves.class));

     /**
      * A {@link Set} of all the known curves names
      */
     public static final Set<String> NAMES =
             Collections.unmodifiableSet(new TreeSet<String>(String.CASE_INSENSITIVE_ORDER) {
                 private static final long serialVersionUID = 1L;    // we're not serializing it

                 {
                     for (ECCurves c : VALUES) {
                         add(c.getName());
                     }
                 }
             });

     /**
      * A {@link Set} of all the known curves key types
      */
     public static final Set<String> KEY_TYPES =
             Collections.unmodifiableSet(new TreeSet<String>(String.CASE_INSENSITIVE_ORDER) {
                 private static final long serialVersionUID = 1L;    // we're not serializing it

                 {
                     for (ECCurves c : VALUES) {
                         add(c.getKeyType());
                     }
                 }
             });

     public static final Comparator<ECCurves> BY_KEY_SIZE = new Comparator<ECCurves>() {
         @Override
         public int compare(ECCurves o1, ECCurves o2) {
             int k1 = (o1 == null) ? Integer.MAX_VALUE : o1.getKeySize();
             int k2 = (o2 == null) ? Integer.MAX_VALUE : o2.getKeySize();
             return Integer.compare(k1, k2);
         }
     };

     public static final List<ECCurves> SORTED_KEY_SIZE =
             Collections.unmodifiableList(
                     new ArrayList<ECCurves>(VALUES) {
                         // Not serializing it
                         private static final long serialVersionUID = 1L;

                         {
                             Collections.sort(this, BY_KEY_SIZE);
                         }
                     });
     private final String name;
     private final String keyType;
     private final ECParameterSpec params;
     private final int keySize;
     private final int numOctets;
     private final DigestFactory digestFactory;

     ECCurves(String name, ECParameterSpec params, int numOctets, DigestFactory digestFactory) {
         this.name = ValidateUtils.checkNotNullAndNotEmpty(name, "No curve name");
         this.keyType = Constants.ECDSA_SHA2_PREFIX + name;
         this.params = ValidateUtils.checkNotNull(params, "No EC params for %s", name);
         this.keySize = getCurveSize(params);
         this.numOctets = numOctets;
         this.digestFactory = ValidateUtils.checkNotNull(digestFactory, "No digestFactory");
     }

     @Override   // The curve name
     public final String getName() {
         return name;
     }

     /**
      * @return The standard key type used to represent this curve
      */
     public final String getKeyType() {
         return keyType;
     }

     @Override
     public final boolean isSupported() {
         return SecurityUtils.hasEcc() && digestFactory.isSupported();
     }

     public final ECParameterSpec getParameters() {
         return params;
     }

     /**
      * @return The size (in bits) of the key
      */
     public final int getKeySize() {
         return keySize;
     }

     /**
      * @return The number of octets used to represent the point(s) for the curve
      */
     public final int getNumPointOctets() {
         return numOctets;
     }

     /**
      * @return The {@link Digest} to use when hashing the curve's parameters
      */
     public final Digest getDigestForParams() {
         return digestFactory.create();
     }

     /**
      * @param type The key type value - ignored if {@code null}/empty
      * @return The matching {@link ECCurves} constant - {@code null} if
      * no match found case <U>insensitive</U>
      */
     public static ECCurves fromKeyType(String type) {
         if (GenericUtils.isEmpty(type)) {
             return null;
         }

         for (ECCurves c : VALUES) {
             if (type.equalsIgnoreCase(c.getKeyType())) {
                 return c;
             }
         }

         return null;
     }

     /**
      * @param name The curve name (case <U>insensitive</U> - ignored if
      *             {@code null}/empty
      * @return The matching {@link ECCurves} instance - {@code null} if no
      * match found
      */
     public static ECCurves fromCurveName(String name) {
         return NamedResource.Utils.findByName(name, String.CASE_INSENSITIVE_ORDER, VALUES);
     }

     /**
      * @param params The curve's {@link ECParameterSpec} - ignored if {@code null}
      * @return The matching {@link ECCurves} value - {@code null} if no match found
      * @see #getCurveSize(ECParameterSpec)
      * @see #fromCurveSize(int)
      */
     public static ECCurves fromCurveParameters(ECParameterSpec params) {
         if (params == null) {
             return null;
         } else {
             return fromCurveSize(getCurveSize(params));
         }
     }

     /**
      * @param keySize The key size (in bits)
      * @return The matching {@link ECCurves} value - {@code null} if no
      * match found
      */
     public static ECCurves fromCurveSize(int keySize) {
         if (keySize <= 0) {
             return null;
         }

         for (ECCurves c : VALUES) {
             if (keySize == c.getKeySize()) {
                 return c;
             }
         }

         return null;
     }

     /**
      * @param params The curve's {@link ECParameterSpec}
      * @return The curve's key size in bits
      * @throws IllegalArgumentException if invalid parameters provided
      */
     public static int getCurveSize(ECParameterSpec params) {
         EllipticCurve curve = ValidateUtils.checkNotNull(params, "No EC params").getCurve();
         ECField field = ValidateUtils.checkNotNull(curve, "No EC curve").getField();
         return ValidateUtils.checkNotNull(field, "No EC field").getFieldSize();
     }

     public static byte[] encodeECPoint(ECPoint group, ECParameterSpec params) {
         return encodeECPoint(group, params.getCurve());
     }

     public static byte[] encodeECPoint(ECPoint group, EllipticCurve curve) {
         // M has len 2 ceil(log_2(q)/8) + 1 ?
         int elementSize = (curve.getField().getFieldSize() + 7) / 8;
         byte[] m = new byte[2 * elementSize + 1];

         // Uncompressed format
         m[0] = 0x04;

         byte[] affineX = removeLeadingZeroes(group.getAffineX().toByteArray());
         System.arraycopy(affineX, 0, m, 1 + elementSize - affineX.length, affineX.length);

         byte[] affineY = removeLeadingZeroes(group.getAffineY().toByteArray());
         System.arraycopy(affineY, 0, m, 1 + elementSize + elementSize - affineY.length, affineY.length);

         return m;
     }

     private static byte[] removeLeadingZeroes(byte[] input) {
         if (input[0] != 0x00) {
             return input;
         }

         int pos = 1;
         while (pos < input.length - 1 && input[pos] == 0x00) {
             pos++;
         }

         byte[] output = new byte[input.length - pos];
         System.arraycopy(input, pos, output, 0, output.length);
         return output;
     }

     public static final class Constants {
         /**
          * Standard prefix of NISTP key types when encoded
          */
         public static final String ECDSA_SHA2_PREFIX = "ecdsa-sha2-";

         public static final String NISTP256 = "nistp256";
         public static final String NISTP384 = "nistp384";
         public static final String NISTP521 = "nistp521";
     }
 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you under the Apache License, Version 2.0 (the
	* "License"); you may not use this file except in compliance
	* with the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing,
	* software distributed under the License is distributed on an
	* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	* KIND, either express or implied. See the License for the
	* specific language governing permissions and limitations
	* under the License.
	*/
	package org.apache.sshd.common.cipher;

	import java.math.BigInteger;
	import java.security.spec.ECField;
	import java.security.spec.ECFieldFp;
	import java.security.spec.ECParameterSpec;
	import java.security.spec.ECPoint;
	import java.security.spec.EllipticCurve;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.Comparator;
	import java.util.EnumSet;
	import java.util.List;
	import java.util.Set;
	import java.util.TreeSet;

	import org.apache.sshd.common.NamedResource;
	import org.apache.sshd.common.OptionalFeature;
	import org.apache.sshd.common.digest.BuiltinDigests;
	import org.apache.sshd.common.digest.Digest;
	import org.apache.sshd.common.digest.DigestFactory;
	import org.apache.sshd.common.util.GenericUtils;
	import org.apache.sshd.common.util.SecurityUtils;
	import org.apache.sshd.common.util.ValidateUtils;

	/**
	* Utilities for working with elliptic curves.
	*
	* @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
	*/
	public enum ECCurves implements NamedResource, OptionalFeature {
	nistp256(Constants.NISTP256,
	new ECParameterSpec(
	new EllipticCurve(
	new ECFieldFp(new BigInteger("FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF", 16)),
	new BigInteger("FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFC", 16),
	new BigInteger("5ac635d8aa3a93e7b3ebbd55769886bc651d06b0cc53b0f63bce3c3e27d2604b", 16)),
	new ECPoint(
	new BigInteger("6B17D1F2E12C4247F8BCE6E563A440F277037D812DEB33A0F4A13945D898C296", 16),
	new BigInteger("4FE342E2FE1A7F9B8EE7EB4A7C0F9E162BCE33576B315ECECBB6406837BF51F5", 16)),
	new BigInteger("FFFFFFFF00000000FFFFFFFFFFFFFFFFBCE6FAADA7179E84F3B9CAC2FC632551", 16),
	1),
	32,
	BuiltinDigests.sha256),
	nistp384(Constants.NISTP384,
	new ECParameterSpec(
	new EllipticCurve(
	new ECFieldFp(new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFFFF0000000000000000FFFFFFFF", 16)),
	new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFFFF0000000000000000FFFFFFFC", 16),
	new BigInteger("B3312FA7E23EE7E4988E056BE3F82D19181D9C6EFE8141120314088F5013875AC656398D8A2ED19D2A85C8EDD3EC2AEF", 16)),
	new ECPoint(
	new BigInteger("AA87CA22BE8B05378EB1C71EF320AD746E1D3B628BA79B9859F741E082542A385502F25DBF55296C3A545E3872760AB7", 16),
	new BigInteger("3617DE4A96262C6F5D9E98BF9292DC29F8F41DBD289A147CE9DA3113B5F0B8C00A60B1CE1D7E819D7A431D7C90EA0E5F", 16)),
	new BigInteger("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFC7634D81F4372DDF581A0DB248B0A77AECEC196ACCC52973", 16),
	1),
	48,
	BuiltinDigests.sha384),
	nistp521(Constants.NISTP521,
	new ECParameterSpec(
	new EllipticCurve(
	new ECFieldFp(new BigInteger("01FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"
	+ "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF", 16)),
	new BigInteger("01FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"
	+ "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFC", 16),
	new BigInteger("0051953EB9618E1C9A1F929A21A0B68540EEA2DA725B99B315F3B8B489918EF109E156193951"
	+ "EC7E937B1652C0BD3BB1BF073573DF883D2C34F1EF451FD46B503F00", 16)),
	new ECPoint(
	new BigInteger("00C6858E06B70404E9CD9E3ECB662395B4429C648139053FB521F828AF606B4D3DBAA14B5E77"
	+ "EFE75928FE1DC127A2FFA8DE3348B3C1856A429BF97E7E31C2E5BD66", 16),
	new BigInteger("011839296A789A3BC0045C8A5FB42C7D1BD998F54449579B446817AFBD17273E662C97EE7299"
	+ "5EF42640C550B9013FAD0761353C7086A272C24088BE94769FD16650", 16)),
	new BigInteger("01FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFA51868783BF2F966B"
	+ "7FCC0148F709A5D03BB5C9B8899C47AEBB6FB71E91386409", 16),
	1),
	66,
	BuiltinDigests.sha512);

	/**
	* A {@link Set} of all the known curves
	*/
	public static final Set<ECCurves> VALUES =
	Collections.unmodifiableSet(EnumSet.allOf(ECCurves.class));

	/**
	* A {@link Set} of all the known curves names
	*/
	public static final Set<String> NAMES =
	Collections.unmodifiableSet(new TreeSet<String>(String.CASE_INSENSITIVE_ORDER) {
	private static final long serialVersionUID = 1L; // we're not serializing it

	{
	for (ECCurves c : VALUES) {
	add(c.getName());
	}
	}
	});

	/**
	* A {@link Set} of all the known curves key types
	*/
	public static final Set<String> KEY_TYPES =
	Collections.unmodifiableSet(new TreeSet<String>(String.CASE_INSENSITIVE_ORDER) {
	private static final long serialVersionUID = 1L; // we're not serializing it

	{
	for (ECCurves c : VALUES) {
	add(c.getKeyType());
	}
	}
	});

	public static final Comparator<ECCurves> BY_KEY_SIZE = new Comparator<ECCurves>() {
	@Override
	public int compare(ECCurves o1, ECCurves o2) {
	int k1 = (o1 == null) ? Integer.MAX_VALUE : o1.getKeySize();
	int k2 = (o2 == null) ? Integer.MAX_VALUE : o2.getKeySize();
	return Integer.compare(k1, k2);
	}
	};

	public static final List<ECCurves> SORTED_KEY_SIZE =
	Collections.unmodifiableList(
	new ArrayList<ECCurves>(VALUES) {
	// Not serializing it
	private static final long serialVersionUID = 1L;

	{
	Collections.sort(this, BY_KEY_SIZE);
	}
	});
	private final String name;
	private final String keyType;
	private final ECParameterSpec params;
	private final int keySize;
	private final int numOctets;
	private final DigestFactory digestFactory;

	ECCurves(String name, ECParameterSpec params, int numOctets, DigestFactory digestFactory) {
	this.name = ValidateUtils.checkNotNullAndNotEmpty(name, "No curve name");
	this.keyType = Constants.ECDSA_SHA2_PREFIX + name;
	this.params = ValidateUtils.checkNotNull(params, "No EC params for %s", name);
	this.keySize = getCurveSize(params);
	this.numOctets = numOctets;
	this.digestFactory = ValidateUtils.checkNotNull(digestFactory, "No digestFactory");
	}

	@Override // The curve name
	public final String getName() {
	return name;
	}

	/**
	* @return The standard key type used to represent this curve
	*/
	public final String getKeyType() {
	return keyType;
	}

	@Override
	public final boolean isSupported() {
	return SecurityUtils.hasEcc() && digestFactory.isSupported();
	}

	public final ECParameterSpec getParameters() {
	return params;
	}

	/**
	* @return The size (in bits) of the key
	*/
	public final int getKeySize() {
	return keySize;
	}

	/**
	* @return The number of octets used to represent the point(s) for the curve
	*/
	public final int getNumPointOctets() {
	return numOctets;
	}

	/**
	* @return The {@link Digest} to use when hashing the curve's parameters
	*/
	public final Digest getDigestForParams() {
	return digestFactory.create();
	}

	/**
	* @param type The key type value - ignored if {@code null}/empty
	* @return The matching {@link ECCurves} constant - {@code null} if
	* no match found case <U>insensitive</U>
	*/
	public static ECCurves fromKeyType(String type) {
	if (GenericUtils.isEmpty(type)) {
	return null;
	}

	for (ECCurves c : VALUES) {
	if (type.equalsIgnoreCase(c.getKeyType())) {
	return c;
	}
	}

	return null;
	}

	/**
	* @param name The curve name (case <U>insensitive</U> - ignored if
	* {@code null}/empty
	* @return The matching {@link ECCurves} instance - {@code null} if no
	* match found
	*/
	public static ECCurves fromCurveName(String name) {
	return NamedResource.Utils.findByName(name, String.CASE_INSENSITIVE_ORDER, VALUES);
	}

	/**
	* @param params The curve's {@link ECParameterSpec} - ignored if {@code null}
	* @return The matching {@link ECCurves} value - {@code null} if no match found
	* @see #getCurveSize(ECParameterSpec)
	* @see #fromCurveSize(int)
	*/
	public static ECCurves fromCurveParameters(ECParameterSpec params) {
	if (params == null) {
	return null;
	} else {
	return fromCurveSize(getCurveSize(params));
	}
	}

	/**
	* @param keySize The key size (in bits)
	* @return The matching {@link ECCurves} value - {@code null} if no
	* match found
	*/
	public static ECCurves fromCurveSize(int keySize) {
	if (keySize <= 0) {
	return null;
	}

	for (ECCurves c : VALUES) {
	if (keySize == c.getKeySize()) {
	return c;
	}
	}

	return null;
	}

	/**
	* @param params The curve's {@link ECParameterSpec}
	* @return The curve's key size in bits
	* @throws IllegalArgumentException if invalid parameters provided
	*/
	public static int getCurveSize(ECParameterSpec params) {
	EllipticCurve curve = ValidateUtils.checkNotNull(params, "No EC params").getCurve();
	ECField field = ValidateUtils.checkNotNull(curve, "No EC curve").getField();
	return ValidateUtils.checkNotNull(field, "No EC field").getFieldSize();
	}

	public static byte[] encodeECPoint(ECPoint group, ECParameterSpec params) {
	return encodeECPoint(group, params.getCurve());
	}

	public static byte[] encodeECPoint(ECPoint group, EllipticCurve curve) {
	// M has len 2 ceil(log_2(q)/8) + 1 ?
	int elementSize = (curve.getField().getFieldSize() + 7) / 8;
	byte[] m = new byte[2 * elementSize + 1];

	// Uncompressed format
	m[0] = 0x04;

	byte[] affineX = removeLeadingZeroes(group.getAffineX().toByteArray());
	System.arraycopy(affineX, 0, m, 1 + elementSize - affineX.length, affineX.length);

	byte[] affineY = removeLeadingZeroes(group.getAffineY().toByteArray());
	System.arraycopy(affineY, 0, m, 1 + elementSize + elementSize - affineY.length, affineY.length);

	return m;
	}

	private static byte[] removeLeadingZeroes(byte[] input) {
	if (input[0] != 0x00) {
	return input;
	}

	int pos = 1;
	while (pos < input.length - 1 && input[pos] == 0x00) {
	pos++;
	}

	byte[] output = new byte[input.length - pos];
	System.arraycopy(input, pos, output, 0, output.length);
	return output;
	}

	public static final class Constants {
	/**
	* Standard prefix of NISTP key types when encoded
	*/
	public static final String ECDSA_SHA2_PREFIX = "ecdsa-sha2-";

	public static final String NISTP256 = "nistp256";
	public static final String NISTP384 = "nistp384";
	public static final String NISTP521 = "nistp521";
	}
	}