openssl GCM 设置 认证标记长度 函数
时间: 2023-12-20 17:13:16 浏览: 36
您可以使用openssl库中的函数 EVP_CIPHER_CTX_ctrl() 来设置GCM的认证标记长度。该函数的第三个参数应该设置为EVP_CTRL_GCM_SET_TAG_LEN,第四个参数设置为所需的认证标记长度。例如,要将认证标记长度设置为16字节,您可以使用以下代码:
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG_LEN, 16, NULL);
相关问题
openssl 初始化GCM 算法设置认证认证标记长度
好的,你想知道如何使用 OpenSSL 初始化 GCM 算法并设置认证标记长度。首先,你需要选择一个适合的密钥大小和 IV 大小,并将其传递给 EVP_CIPHER_CTX_init() 函数以初始化加密上下文对象。接下来,你需要调用 EVP_EncryptInit_ex() 函数,指定加密算法以及 GCM 模式,并设置认证标记长度。具体方法如下:
```
EVP_CIPHER_CTX *ctx;
unsigned char *key, *iv;
int key_len, iv_len, tag_len;
// 初始化加密上下文对象
ctx = EVP_CIPHER_CTX_new();
EVP_CIPHER_CTX_init(ctx);
// 设置密钥和 IV
key = (unsigned char *)"0123456789ABCDEF";
key_len = strlen((const char *)key);
iv = (unsigned char *)"01234567";
iv_len = strlen((const char *)iv);
// 初始化加密算法和 GCM 模式
EVP_EncryptInit_ex(ctx, EVP_aes_128_gcm(), NULL, NULL, NULL);
// 设置认证标记长度
tag_len = 16;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, tag_len, NULL);
// 执行加密操作
// ...
// 清理加密上下文对象
EVP_CIPHER_CTX_cleanup(ctx);
```
在这个示例中,我们使用了 128 位的 AES 密钥和 64 位的 IV,以及 16 字节的认证标记长度。你可以根据自己的需要修改这些参数。
openssl GCM
OpenSSL is a widely-used open-source cryptographic library that provides support for various cryptographic algorithms, including the GCM (Galois/Counter Mode) encryption mode.
GCM is an authenticated encryption mode that provides both confidentiality and integrity. It combines the Counter (CTR) mode of encryption with a universal hash function called Galois Message Authentication Code (GMAC). GCM is commonly used for secure communication protocols like TLS.
To use GCM with OpenSSL, you can utilize the EVP (Envelope) API provided by OpenSSL. Here's an example of how you can use OpenSSL to perform GCM encryption and decryption:
```c
#include <openssl/evp.h>
void encrypt_decrypt_gcm(const unsigned char* key, const unsigned char* iv, const unsigned char* aad,
const unsigned char* ciphertext, int ciphertext_len, unsigned char* tag,
unsigned char* plaintext) {
EVP_CIPHER_CTX* ctx;
int len;
int plaintext_len;
// Create and initialize the context
ctx = EVP_CIPHER_CTX_new();
EVP_EncryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, NULL, NULL);
// Set the key and IV
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_KEY_LEN, 256, NULL);
EVP_EncryptInit_ex(ctx, NULL, NULL, key, iv);
// Set the AAD (Additional Authenticated Data)
EVP_EncryptUpdate(ctx, NULL, &len, aad, sizeof(aad));
// Perform the encryption
EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len);
// Finalize the encryption (generates the authentication tag)
EVP_EncryptFinal_ex(ctx, ciphertext + len, &len);
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, 16, tag);
// Cleanup
EVP_CIPHER_CTX_free(ctx);
}
int main() {
unsigned char key[32]; // 256-bit key
unsigned char iv[12]; // 96-bit IV
unsigned char aad[16]; // Additional Authenticated Data
unsigned char ciphertext[128];
unsigned char tag[16];
unsigned char plaintext[128];
// Initialize the key, IV, AAD, and plaintext
encrypt_decrypt_gcm(key, iv, aad, ciphertext, sizeof(ciphertext), tag, plaintext);
return 0;
}
```
In this example, you would need to replace the placeholders for the key, IV, AAD, ciphertext, and plaintext with the actual data you want to use. Additionally, make sure to include the necessary OpenSSL headers and link against the OpenSSL library when compiling.
This is just a basic example and it's important to use proper cryptographic practices and ensure the security of your implementation. It's recommended to refer to the OpenSSL documentation and consult cryptographic experts for more guidance on using GCM with OpenSSL.
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