關鍵代碼：
public String decrypt(String encryptedData, String sessionKey, String iv, String encodingFormat) throws Exception {
try {
Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
BASE64Decoder base64Decoder = new BASE64Decoder();
byte[] _encryptedData = base64Decoder.decodeBuffer(encryptedData);
byte[] _sessionKey = base64Decoder.decodeBuffer(sessionKey);
byte[] _iv = base64Decoder.decodeBuffer(iv);
SecretKeySpec secretKeySpec = new SecretKeySpec(_sessionKey, "AES");
IvParameterSpec ivParameterSpec = new IvParameterSpec(_iv);
cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
byte[] original = cipher.doFinal(_encryptedData);
byte[] bytes = WxPKCS7Encoder.decode(original);
String originalString = new String(bytes, encodingFormat); return originalString;
} catch (Exception ex) {
return null;
}
}
依賴類 WxPKCS7Encoder.javaclass WxPKCS7Encoder {
static Charset CHARSET = Charset.forName("utf-8");
static int BLOCK_SIZE = 32;
/**
* 獲得對明文進行補位填充的字節.
*
* @param count 需要進行填充補位操作的明文字節個數
* @return 補齊用的字節數組
*/
static byte[] encode(int count) {
// 計算需要填充的位數
int amountToPad = BLOCK_SIZE - (count % BLOCK_SIZE);
if (amountToPad == 0) {
amountToPad = BLOCK_SIZE;
}
// 獲得補位所用的字符
char padChr = chr(amountToPad);
String tmp = new String();
for (int index = 0; index < amountToPad; index++) {
tmp += padChr;
}
return tmp.getBytes(CHARSET);
}
/**
* 刪除解密后明文的補位字符
*
* @param decrypted 解密后的明文
* @return 刪除補位字符后的明文
*/
static byte[] decode(byte[] decrypted) {
int pad = (int) decrypted[decrypted.length - 1];
if (pad < 1 || pad > 32) {
pad = 0;
}
return Arrays.copyOfRange(decrypted, 0, decrypted.length - pad);
}
/**
* 將數字轉化成ASCII碼對應的字符，用于對明文進行補碼
*
* @param a 需要轉化的數字
* @return 轉化得到的字符
*/
static char chr(int a) {
byte target = (byte) (a & 0xFF);
return (char) target;
}
}
jdk版本1.8
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