[英]JAVA ANDROID AES CFB NOPADDING
我使用以下代碼創建了一個Java文件,該代碼對字符串進行加密或解密:
public class Aes {
public static String encrypt(String seed, String cleartext)
throws Exception {
byte[] rawKey = getRawKey(seed.getBytes());
byte[] result = encrypt(rawKey, cleartext.getBytes());
return toHex(result);
}
public static String decrypt(String seed, String encrypted)
throws Exception {
byte[] rawKey = getRawKey(seed.getBytes());
byte[] enc = toByte(encrypted);
byte[] result = decrypt(rawKey, enc);
return new String(result);
}
private static byte[] getRawKey(byte[] seed) throws Exception {
KeyGenerator kgen = KeyGenerator.getInstance("AES");
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
sr.setSeed(seed);
kgen.init(128, sr); // 192 and 256 bits may not be available
SecretKey skey = kgen.generateKey();
byte[] raw = skey.getEncoded();
return raw;
}
private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
byte[] iv = new byte[] { 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xA, 0xB, 0xC, 0xD, 0xE, 0xF };
IvParameterSpec ivSpec = new IvParameterSpec(iv);
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES/CFB/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec, ivSpec);
byte[] encrypted = cipher.doFinal(clear);
return encrypted;
}
private static byte[] decrypt(byte[] raw, byte[] encrypted)
throws Exception {
byte[] iv = new byte[] { 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xA, 0xB, 0xC, 0xD, 0xE, 0xF };
IvParameterSpec ivSpec = new IvParameterSpec(iv);
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES/CFB/NoPadding");
cipher.init(Cipher.DECRYPT_MODE, skeySpec, ivSpec);
byte[] decrypted = cipher.doFinal(encrypted);
return decrypted;
}
public static String toHex(String txt) {
return toHex(txt.getBytes());
}
public static String fromHex(String hex) {
return new String(toByte(hex));
}
public static byte[] toByte(String hexString) {
int len = hexString.length() / 2;
byte[] result = new byte[len];
for (int i = 0; i < len; i++)
result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2),
16).byteValue();
return result;
}
public static String toHex(byte[] buf) {
if (buf == null)
return "";
StringBuffer result = new StringBuffer(2 * buf.length);
for (int i = 0; i < buf.length; i++) {
appendHex(result, buf[i]);
}
return result.toString();
}
private final static String HEX = "0123456789ABCDEF";
private static void appendHex(StringBuffer sb, byte b) {
sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
}
}
我已成功嘗試加密字符串,但未將其解密...請幫助我。 這是我之前測試過的加密示例代碼:
String data = "HELP";
String enc = "";
try {
enc = Aes.encrypt("1234567890", data);
Log.i("ENCRYPT", data + " TO " + enc);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
結果是:48F1880B
我的問題是,如何解密? 我使用上面的代碼進行了測試,但結果不等於純文本! 請幫我...
以下示例類應為您提供所有標記為步驟的正確加密/解密方法的良好參考:
public class AES {
public static SecretKey generateAESKey(int bits) throws NoSuchAlgorithmException{
//This method is provided as to securely generate a AES key of the given length.
//In practice you can specify your own SecureRandom instance.
KeyGenerator kgen = KeyGenerator.getInstance("AES");
kgen.init(bits);
return kgen.generateKey();
}
public static byte[] encrypt(SecretKey key, byte[] plaintext) throws Exception{
//In practice you should specify your SecureRandom implementation.
SecureRandom rnd = new SecureRandom();
//Generate random IV of 128-bit (AES block size)
byte[] IV = new byte[128 / 8];
rnd.nextBytes(IV);
IvParameterSpec IVSpec = new IvParameterSpec(IV);
//Create the cipher object to perform AES operations.
//Specify Advanced Encryption Standard - Cipher Feedback Mode - No Padding
Cipher AESCipher = Cipher.getInstance("AES/CFB/NoPadding");
//Initialize the Cipher with the key and initialization vector.
AESCipher.init(Cipher.ENCRYPT_MODE, key, IVSpec);
//Encrypts the plaintext data
byte[] ciphertext = AESCipher.doFinal(plaintext);
/*
* The IV must now be transferred with the ciphertext somehow. The easiest
* way to accomplish this would be to prepend the IV to the ciphertext
* message.
*/
//Allocate new array to hold ciphertext + IV
byte[] output = new byte[ciphertext.length + (128 / 8)];
//Copy the respective parts into the array.
System.arraycopy(IV, 0, output, 0, IV.length);
System.arraycopy(ciphertext, 0, output, IV.length, ciphertext.length);
return output;
}
public static byte[] decrypt(SecretKey key, byte[] IV, byte[] ciphertext) throws Exception{
//Create the cipher object to perform AES operations.
//Specify Advanced Encryption Standard - Cipher Feedback Mode - No Padding
Cipher AESCipher = Cipher.getInstance("AES/CFB/NoPadding");
//Create the IvParameterSpec object from the raw IV
IvParameterSpec IVSpec = new IvParameterSpec(IV);
//Initialize the Cipher with the key and initialization vector.
AESCipher.init(Cipher.DECRYPT_MODE, key, IVSpec);
//Decrypts the ciphertext data
byte[] plaintext = AESCipher.doFinal(ciphertext);
return plaintext;
}
public static void main(String[] args) throws Exception{
//Demo the program
String sPlaintext = "rainbows"; //String plaintext
byte[] rPlaintext = sPlaintext.getBytes(Charset.forName("UTF-8")); //Raw byte array plaintext
//We first need to generate a key of 128-bit
SecretKey key = generateAESKey(128);
//Encrypt the plaintext
byte[] output = encrypt(key, rPlaintext);
// ----------------- //
//Extract the IV from the encryption output
byte[] IV = new byte[128 / 8];
byte[] ciphertext = new byte[output.length - (128 / 8)];
System.arraycopy(output, 0, IV, 0, IV.length);
System.arraycopy(output, IV.length, ciphertext, 0, ciphertext.length);
//Decrypt the ciphertext
byte[] dPlaintext = decrypt(key, IV, ciphertext);
String decryptedMessage = new String(dPlaintext, Charset.forName("UTF-8"));
//Print stuff out
System.out.println("Original message: " + sPlaintext);
System.out.println("Original message bytes: " + Arrays.toString(rPlaintext));
System.out.println("Encryption Output bytes: " + Arrays.toString(output));
System.out.println("Decrypted message bytes: " + Arrays.toString(dPlaintext));
System.out.println("Decrypted message: " + decryptedMessage);
}
}
但是要注意的幾件事:
throws Exception
是不能接受的。 放置它只是為了簡化代碼,切勿在實踐中使用。 盡管不大可能拋出諸如NoSuchAlgorithmException
已檢查異常,但請警惕decrypt()
方法將為解密失敗而拋出異常 (即,錯誤的密鑰/ IV /密文)。
接下來我要講的是,您不應該依賴引發異常的decrypt()
方法來驗證輸入。 這應該是一種具有安全單向哈希函數的函數,例如SHA-2
。
注意如何一次生成用於加密/解密的密鑰。 AES是對稱的分組密碼,這意味着加密和解密使用相同的密鑰 。 請注意這一點,並且不要在加密和解密之間生成新的密鑰 (但是,只要您願意,只要使用相同的密鑰進行解密,就可以為每個加密生成一個新的密鑰)。
問題主要在
public static String toHex(String txt) {
return toHex(txt.getBytes());
}
public static String fromHex(String hex) {
return new String(toByte(hex));
}
public static byte[] toByte(String hexString) {
int len = hexString.length() / 2;
byte[] result = new byte[len];
for (int i = 0; i < len; i++)
result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2),
16).byteValue();
return result;
從Hex String
轉換String
,您不會以前導零進行轉換,即,無論何時轉換char
並且該char
的可能值為零,則十六進制值也為00 ,默認情況下,您的方法將忽略一個零並僅添加十六進制字符串為零
注意:-數字零0
不等於零的十六進制值。十六進制的零值為空字符,請參考ASCII表。
帶前導零 ef1b0030ef
不帶前導零 ef1b030ef
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