置换加密算法2.doc

置换密码算法的原理是不改变明文字符，而是按照某一规则重新排列消息中的比特或字符顺序，才而实现明文信息的加密。置换密码有时又称为换位密码。矩阵换位法是实现置换密码的一种常用方法。它将明文中的字母按照给定的顺序安排在一个矩阵中，然后用根据密钥提供的顺序重新组合矩阵中的字母，从而形成密文。例如，明文为attack begins at five，密钥为cipher，将明文按照每行6个字母的形式排在矩阵中，形成如下形式：根据密钥cipher中各个字母在字母表中出现的先后顺序，给定一个置换：由密钥cipher通过getTheMatrix方法得到f矩阵。根据上面的置换，将原有居住中的字母按照第列、第裂、第裂、第裂、第列、第列的顺序排列，则有下面的形式：这里经过了一点处理就是当输入的字母数不是密钥长度的整数倍时，在输入的备加密字符串加上几个“#”来完成补全，然后参加到加密的过程中去，从而得到如下的密文：a siteaetb vci #agt#knf#其解密过程是根据密钥的字母数作为列数，将密文按照列、行的顺序写出，再根据由 密钥给出的矩阵置换产生新的矩阵，从而恢复明文。 本实验中也使用了上述的测试用例，主要经过两次依据矩阵的变换，都是使用矩阵f中的下面一行中的数值所在列来替换上面一行数值表示的列的值，从而来改变起序列、完成加密。解密中用到groupedSourceij=tempisecretMatrixsecretMatrixj;来完成将原来经过矩阵转变来的字符序列逆转，从而得到起加密前的矩阵。【代码部分】package Practice1;import java.util.Arrays;import java.util.Scanner;public class ReplaceDemo private String sourceString = attack begins at five;private String keyString = cipher;private int secretMatrix;private char groupedSource;private void getSource()/Get the source StringScanner scan = new Scanner(System.in);System.out.print(Please input the string what you want to encrypt:t);sourceString = scan.nextLine();System.out.print(Please input the key string for you:t);keyString = scan.next();public ReplaceDemo()/constructor for this classgetSource();private void groupSourceString()/make groups for sourceString according by the keyStringint sourceLen = sourceString.length();int keyLen = keyString.length();groupedSource = new charsourceLen/keyLen+1keyLen;if (sourceLen%keyLen!=0)for (int i = 0;i (keyLen - sourceLen%keyLen);i+)sourceString += #;sourceLen = sourceString.length();for(int i = 6,j=0;i = sourceLen;i+=keyLen,j+)groupedSourcej = sourceString.substring(i-keyLen, i).toCharArray();private void getTheMatrix()/get the Matrix for the encryptchar temp01 = keyString.toCharArray();secretMatrix = new intkeyString.length();Arrays.sort(temp01);for (int i = 0;i keyString.length();i+)for (int j = 0;jkeyString.length();j+)if (keyString.toCharArray()i=temp01j)secretMatrixi = j;private void changeSourceMatix()groupSourceString();char temp = new chargroupedSource.lengthkeyString.length();for (int i = 0;i groupedSource.length;i+)for (int j = 0;j keyString.length();j+)tempij = groupedSourceij;/请教Java老师for (int i = 0;i groupedSource.length - 1;i+)for (int j = 0;j keyString.length();j+)groupedSourceij = tempisecretMatrixj;private void getEncryptedString()/get the matrix which will be printed.groupSourceString();changeSourceMatix();char temp = new chargroupedSource.lengthkeyString.length();for (int i = 0;i groupedSource.length;i+)for (int j = 0;j keyString.length();j+)tempij = groupedSourceij;for (int i = 0;i groupedSource.length - 1;i+)for (int j = 0;j keyString.length();j+)groupedSourceij = tempisecretMatrixj;public void print1()/print the code have EncryptedgetEncryptedString();for(int i = 0;i keyString.length();i+)for(int j = 0;j groupedSource.length-1;j+)System.out.print(groupedSourceji);System.out.println();/decryption processprivate void groupEncryptedString()int sourceLen = sourceString.length();int keyLen = keyString.length();char temp = new charkeyLensourceLen/keyLen+1;for (int i = 0;i keyLen;i+)tempi = sourceString.substring(i*sourceLen/keyLen, (i+1)*sourceLen/keyLen).toCharArray();groupedSource = new charsourceLen/keyLen+1keyLen;for(int j = 0; j sourceLen/keyLen;j+)for (int i = 0;i keyLen;i+)groupedSourceji = tempij;private void getDecryptString()/get the matrix which will be printed.groupEncryptedString();char temp = new chargroupedSource.lengthkeyString.length();for (int i = 0;i groupedSource.length;i+)for (int j = 0;j keyString.length();j+)tempij = groupedSourceij;for (int i = 0;i groupedSource.length - 1;i+)for (int j = 0;j keyString.length();j+)groupedSourceij = tempisecretMatrixsecretMatrixj;public void print2()/print the code have EncryptedgetDecryptString();for(int j = 0;j groupedSource.length-1;j+)for(int i = 0;i keyString.length();i+)System.out.print(groupedSourceji);System.out.println();public static void main(String args)ReplaceDemo RD = null;Scanner scanin = null;System.out.println(please select the method that you want to operate:t(select “0” for encrypte and select “1” for decrypt.);scanin = new Scanner(System.in);int selected = scanin.nextInt();while(selected=0 | selected=1)RD = new ReplaceDemo();RD.getTheMatrix();if (selected = 0)RD.print1();elseRD.print2();System.out.println(p