publickey.java

手机上进行RSA加密的算法

package rsa;

/**
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2003</p>
 * <p>Company: </p>
 * @author not attributable
 * @version 1.0
 */

public class PublicKey
{
        /** the public modulus */
        protected BigInteger n_;

        /** the public exponent */
        protected BigInteger e_;

        protected PublicKey()
        {
        }

        /**
         * create a public key from a modulus and exponent
         * @param n0 The public modulus
         * @param e0 The public exponent
         */
        public PublicKey( BigInteger n0, BigInteger e0 )
        {
                n_= new BigInteger( n0 );
                e_= new BigInteger( e0 );
        }

        /**
         * create a new public key from an existing key.
         * @param from0 the key to copy.
         */
        public PublicKey( PublicKey from0 )
        {
                copy( from0 );
        }

        /**
         * @return a new BigInteger equal to the public modulus
         */
        public final BigInteger
        n()
        {
                return new BigInteger( n_ );
        }

        /**
         * @return a new BigInteger equal to the public exponent
         */
        public final BigInteger
        e()
        {
                return new BigInteger( e_ );
        }

        /**
         * copies a key if it is an instance of cryptix.security.rsa.PublicKey.
         * @param src this object to copy
         */
        public void
        copy( Object src )
        {
                PublicKey from = (PublicKey)src;
                n_ = new BigInteger( from.n_ );
                e_ = new BigInteger( from.e_ );
        }

        /**
         * tests if an object is equal to this one.
         * @param obj object to test
         * @return true if the object is equal, otherwise false.
         */
        public boolean equals( Object obj )
        {
                if ( obj instanceof PublicKey )
                {
                        PublicKey from = (PublicKey)obj;
                        if ( n_.equals( from.n_ ) && e_.equals( from.e_ ) )
                                return true;
                }
                return false;
        }

        /**
         * gets the key id.
         * @returns The lower 8 bytes of n, the public modulus.
         */
        public final byte[]
        id()
        {
                byte nBuffer[] = n_.toByteArray();
                byte ident[] = new byte[8];
                System.arraycopy( nBuffer, nBuffer.length - 8, ident, 0, 8 );
                return ident;
        }

        /**
         * get the keys fingerprint.
         * @return a MD5 hash of n and e.
         */
 /*       public final byte[]
        fingerPrint()
        {
                byte eBuffer[] = e_.toByteArray();
                byte nBuffer[] = n_.toByteArray();
                MD5 md = new MD5();
                md.add( nBuffer );
                md.add( eBuffer );
                return md.digest();
        }
*/
        /**
         * get the keys bit length.
         * @return the length in bits of n, the public modulus.
         */
        public final int bitLength()
        {
                return n_.bitLength();
        }

        /**
         * encrypts a number with this key.
         * @param plain the number to encrypt.
         * @return an encrypted number.
         */
        public BigInteger
        encrypt( BigInteger plain )
        {
                return new BigInteger( plain ).modExp( e_, n_ );
        }

        /**
         * @return this key in hex.
         */
        public String
        toString()
        {
                return "n:" + n_ + "\ne:" + e_;
        }
}