vignere.java

用JAVA编写的小的JAVA程序,是有关密码转换的.有2种算法.

public class Vignere extends Cipher {


	/* (non-Javadoc)
	 * @see Cipher#encrypt(java.lang.String)
	 */
	public String encrypt(String cleartext) {

		StringBuffer strb = new StringBuffer(cleartext.length());
		char keyc[] = this.getSKey().toCharArray();
		char[] clear = cleartext.toCharArray();

		int posClearALPHABET, posKeyALPHABET;
		int posCipherText;

		for (int i = 0; i < clear.length; i++)
		{

			posClearALPHABET = Character.getNumericValue(clear[i])-Character.getNumericValue(ALPHABET[0]) + 1;
			posKeyALPHABET = Character.getNumericValue(keyc[i % keyc.length])-Character.getNumericValue(ALPHABET[0]);

			posCipherText = (posClearALPHABET+posKeyALPHABET);
			strb.append(ALPHABET[posCipherText]);
		}

		return strb.toString();
	}//END OF METHOD


	/* (non-Javadoc)
	 * @see Cipher#decrypt(java.lang.String)
	 */
	public String decrypt(String ciphertext) {

		StringBuffer strb = new StringBuffer(ciphertext.length());
		char keyc[] = this.getSKey().toCharArray();
		char[] cipher = ciphertext.toCharArray();

		int posClearALPHABET, posKeyALPHABET;
		int posCipherText;

		for (int i = 0; i < cipher.length; i++)
		{
			posCipherText = Character.getNumericValue(cipher[i])-Character.getNumericValue(ALPHABET[0]);
			posKeyALPHABET = Character.getNumericValue(keyc[i % keyc.length])-Character.getNumericValue(ALPHABET[0])+1;

			posClearALPHABET = (posCipherText - posKeyALPHABET) % ALPHABET.length;

			if (posClearALPHABET < 0) posClearALPHABET = ALPHABET.length + posClearALPHABET;

			strb.append(ALPHABET[posClearALPHABET]);

		}

		return strb.toString();
	}
}