以下是一个使用Objective-C实现AES128加密CBC/NoPadding的示例代码：

#import 

NSData *AES128EncryptCBCNoPadding(NSString *key, NSString *iv, NSString *plainText) {
    NSData *keyData = [key dataUsingEncoding:NSUTF8StringEncoding];
    NSData *ivData = [iv dataUsingEncoding:NSUTF8StringEncoding];
    NSData *plainData = [plainText dataUsingEncoding:NSUTF8StringEncoding];
    
    size_t bufferSize = plainData.length + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t encryptedSize = 0;
    CCCryptorStatus result = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                     keyData.bytes, keyData.length,
                                     ivData.bytes,
                                     plainData.bytes, plainData.length,
                                     buffer, bufferSize, &encryptedSize);
    
    if (result == kCCSuccess) {
        NSData *encryptedData = [NSData dataWithBytesNoCopy:buffer length:encryptedSize];
        return encryptedData;
    }
    
    free(buffer);
    return nil;
}

NSString *AES128DecryptCBCNoPadding(NSString *key, NSString *iv, NSData *encryptedData) {
    NSData *keyData = [key dataUsingEncoding:NSUTF8StringEncoding];
    NSData *ivData = [iv dataUsingEncoding:NSUTF8StringEncoding];
    
    size_t bufferSize = encryptedData.length + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t decryptedSize = 0;
    CCCryptorStatus result = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                     keyData.bytes, keyData.length,
                                     ivData.bytes,
                                     encryptedData.bytes, encryptedData.length,
                                     buffer, bufferSize, &decryptedSize);
    
    if (result == kCCSuccess) {
        NSData *decryptedData = [NSData dataWithBytesNoCopy:buffer length:decryptedSize];
        NSString *decryptedText = [[NSString alloc] initWithData:decryptedData encoding:NSUTF8StringEncoding];
        return decryptedText;
    }
    
    free(buffer);
    return nil;
}

使用示例：

NSString *key = @"0123456789abcdef";
NSString *iv = @"0123456789abcdef";
NSString *plainText = @"Hello, World!";
    
NSData *encryptedData = AES128EncryptCBCNoPadding(key, iv, plainText);
NSString *encryptedText = [encryptedData base64EncodedStringWithOptions:0];
NSLog(@"Encrypted Text: %@", encryptedText);
    
NSString *decryptedText = AES128DecryptCBCNoPadding(key, iv, encryptedData);
NSLog(@"Decrypted Text: %@", decryptedText);

请注意，这只是一个简单的示例代码，并不考虑错误处理和安全性。如果要在实际应用中使用加密算法，请确保采取适当的安全措施。