// 先定义一个初始向量的值。
NSString *const kInitVector = @"16-Bytes--String";

// 确定密钥长度，这里选择 AES-128。
size_t const kKeySize = kCCKeySizeAES128;

加密操作

+ (NSString *)encryptAES:(NSString *)content key:(NSString *)key {

    NSData *initVector = [kInitVector dataUsingEncoding:NSUTF8StringEncoding];
    NSData *keyData = [key dataUsingEncoding:NSUTF8StringEncoding];
    NSData *contentData = [content dataUsingEncoding:NSUTF8StringEncoding];
    NSUInteger dataLength = contentData.length;
    
    // 密文长度 <= 明文长度 + BlockSize
    size_t encryptSize = dataLength + kCCBlockSizeAES128;
    void *encryptedBytes = malloc(encryptSize);
    size_t actualOutSize = 0;
    
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
                                          kCCAlgorithmAES,
                                          kCCOptionPKCS7Padding,  // 系统默认使用 CBC，然后指明使用 PKCS7Padding
                                          keyData.bytes,
                                          kKeySize,
                                          initVector.bytes,
                                          contentData.bytes,
                                          dataLength,
                                          encryptedBytes,
                                          encryptSize,
                                          &actualOutSize);
    
    if (cryptStatus == kCCSuccess) {
        // 对加密后的数据进行 base64 编码
        return [[NSData dataWithBytesNoCopy:encryptedBytes length:actualOutSize] base64EncodedStringWithOptions:NSDataBase64EncodingEndLineWithLineFeed];
    }
    free(encryptedBytes);
    return nil;
}

解密操作

+ (NSString *)decryptAES:(NSString *)content key:(NSString *)key {
    // 把 base64 String 转换成 Data
    NSData *contentData = [[NSData alloc] initWithBase64EncodedString:content options:NSDataBase64DecodingIgnoreUnknownCharacters];
    NSUInteger dataLength = contentData.length;
    char keyPtr[kKeySize + 1];
    memset(keyPtr, 0, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    size_t decryptSize = dataLength + kCCBlockSizeAES128;
    void *decryptedBytes = malloc(decryptSize);
    size_t actualOutSize = 0;
    NSData *initVector = [kInitVector dataUsingEncoding:NSUTF8StringEncoding];
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmAES,
                                          kCCOptionPKCS7Padding,
                                          keyPtr,
                                          kKeySize,
                                          initVector.bytes,
                                          contentData.bytes,
                                          dataLength,
                                          decryptedBytes,
                                          decryptSize,
                                          &actualOutSize);
    if (cryptStatus == kCCSuccess) {
        return [[NSString alloc] initWithData:[NSData dataWithBytesNoCopy:decryptedBytes length:actualOutSize] encoding:NSUTF8StringEncoding];
    }
    free(decryptedBytes);
    return nil;
}

【代码下载】

AESCipher-iOS
AES4ObjC-Java-JavaScript/Objective-C/TestAES/

【参考资料】

AES加密 - iOS与 Java 的同步实现
AES加密 - iOS与 Java 的同步实现（转载 + 整理）