我正在写两个程序；一个加密第一个参数中给出的文件，第二个参数中给出一个 ASCII 种子，另一个解密加密文件。该算法在 CBC 流密码模式下使用 AES-128。该文件被读入缓冲区，生成一个 SHA-1 散列并附加到明文，然后加密。种子也是由 SHA-1 产生的。解密程序（使用相同的种子）将消息从摘要中分离出来，并将摘要与本地生成的散列进行比较。到目前为止，这两个程序都非常适合 .txt 文件，但如果我尝试加密/解密 .jpg 或 .png 文件，原始图像剩下的只是顶部的一小部分 - 其余的只是随机颜色。.zip 文件损坏。
我的代码很大，很抱歉。
加密：
public class secureFile
{
private static SecretKeySpec sec_key_spec;
private static Cipher sec_cipher;
private static final int SIZE_LIMIT = 1024;
private static final int SHA1_SIZE = 20;
// encryption function
public static byte[] encrypt(byte[] plaintext) throws Exception
{
byte[] encrypted = null;
byte[] iv = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
IvParameterSpec ivspec = new IvParameterSpec(iv);
try {
//set cipher object to encrypt mode
sec_cipher.init(Cipher.ENCRYPT_MODE, sec_key_spec, ivspec);
//create ciphertext
encrypted = sec_cipher.doFinal(plaintext);
}
catch(Exception e) {
System.out.println(e);
}
return encrypted;
}
//creates SHA-1 message digest
public static byte[] createDigest(byte[] message) throws Exception
{
byte[] hash = null;
try{
//create message digest object
MessageDigest sha1 = MessageDigest.getInstance("SHA1");
//make message digest
hash = sha1.digest(message);
}
catch(NoSuchAlgorithmException nsae) {
System.out.println(nsae);
}
return hash;
}
public static void main (String args[]) throws Exception
{
byte[] key;
byte[] key128;
FileInputStream mFile;
FileOutputStream cFile;
byte[] ciphertext;
byte[] plaintext;
byte[] sha1_hash;
byte[] message;
String cFilename;
int file_size;
try {
//gets filenames and fileinput
String[] mFilename = args[0].split("\\.(?=[^\\.]+$)");
cFilename = mFilename[0] + "EN." + mFilename[1];
mFile = new FileInputStream(mFilename[0] + "." + mFilename[1]);
//limits buffer size to 1024
file_size = mFile.available();
if (file_size > SIZE_LIMIT) {
file_size = SIZE_LIMIT;
}
//reads message file in buffer
message = new byte[file_size];
mFile.read(message);
mFile.close();
//creates sha1 digest from message
sha1_hash = createDigest(message);
//combines message and digest
plaintext = new byte[file_size + SHA1_SIZE];
for (int i = 0; i < file_size; i++) {
plaintext[i] = message[i];
}
for (int j = 0; j < SHA1_SIZE; j++) {
plaintext[file_size + j] = sha1_hash[j];
}
//generates key
key = createDigest(args[1].getBytes("us-ascii"));
key128 = Arrays.copyOfRange(key, 0, 16);
sec_key_spec = new SecretKeySpec(key128, "AES");
//enciphers the plaintext
sec_cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
ciphertext = encrypt(plaintext);
//copies ciphertext to file
cFile = new FileOutputStream(cFilename);
cFile.write(ciphertext);
cFile.close();
}
catch (Exception e) {
System.out.println(e);
}
}
}
解密文件：
import java.io.*;
import java.util.*;
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;
public class decryptFile
{
private static SecretKeySpec sec_key_spec = null;
private static Cipher sec_cipher = null;
private static final int SHA1_SIZE = 20;
//decryption function
public static byte[] decrypt(byte[] ciphertext) throws Exception{
byte[] decrypted = null;
byte[] iv = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
IvParameterSpec ivspec = new IvParameterSpec(iv);
try{
//set cipher to decrypt mode
sec_cipher.init(Cipher.DECRYPT_MODE, sec_key_spec, ivspec);
//do decryption
decrypted = sec_cipher.doFinal(ciphertext);
}
catch (BadPaddingException b)
{
sec_cipher.init(Cipher.ENCRYPT_MODE, sec_key_spec, ivspec);
decrypted = sec_cipher.doFinal(ciphertext);
}
catch(Exception e){
System.out.println(e);
}
return decrypted;
}
//creates digest
public static byte[] createDigest(byte[] message) throws Exception
{
byte[] hash = null;
try{
//create message digest object
MessageDigest sha1 = MessageDigest.getInstance("SHA1");
//make message digest
hash = sha1.digest(message);
}
catch(NoSuchAlgorithmException nsae) {
System.out.println(nsae);
}
return hash;
}
//compares two digests
public static String compareDigests(byte[] digest, byte[] local_digest)
{
for (int i = 0; i < SHA1_SIZE; i++)
{
if (digest[i] != local_digest[i]) {
return "Digests don't match; your file may have been tampered with.";
}
}
return "Digests match!";
}
public static void main (String args[])
{
FileInputStream cFile;
FileOutputStream mFile;
byte[] key;
byte[] key128;
byte[] ciphertext;
byte[] decrypted;
byte[] message;
byte[] digest;
byte[] local_digest;
byte[] local_digest2;
String mFilename;
int file_size;
try {
//obtains filenames
String[] cFilename = args[0].split("\\.(?=[^\\.]+$)");
mFilename = cFilename[0] + "DE." + cFilename[1];
cFile = new FileInputStream(cFilename[0] + "." + cFilename[1]);
//reads ciphertext file
cFile = new FileInputStream(cFilename[0] + "." + cFilename[1]);
ciphertext = new byte[cFile.available()];
cFile.read(ciphertext);
cFile.close();
//generates key
key = createDigest(args[1].getBytes("us-ascii"));
key128 = Arrays.copyOfRange(key, 0, 16);
sec_key_spec = new SecretKeySpec(key128, "AES");
//deciphers the plaintext
sec_cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
decrypted = decrypt(ciphertext);
//splits plaintext between message and digest
file_size = decrypted.length;
message = Arrays.copyOfRange(decrypted, 0, (file_size - SHA1_SIZE));
digest = Arrays.copyOfRange(decrypted, (file_size - SHA1_SIZE), file_size);
//compares digests
local_digest = createDigest(message);
System.out.println(compareDigests(digest, local_digest));
//copies message to file
mFile = new FileOutputStream(mFilename);
mFile.write(message);
mFile.close();
}
catch (Exception e) {
System.out.println(e);
}
}
}
我非常感谢你能给我的任何帮助。谢谢！