String 128bit
时间: 2023-06-30 08:17:32 浏览: 44
如果你需要使用字符串生成一个128位的密钥,可以使用如下代码:
```
String key = "my secret key";
byte[] keyBytes = Arrays.copyOf(key.getBytes("UTF-8"), 16);
SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");
```
这个代码块中,我们首先将字符串`"my secret key"`转换为byte数组,并使用UTF-8编码。由于AES算法需要一个16字节的密钥,因此我们使用`Arrays.copyOf`方法将byte数组的长度扩展或缩短到16字节。最后,我们使用`SecretKeySpec`类将byte数组转换为一个`SecretKey`对象。
需要注意的是,使用字符串生成密钥并不是一种安全的方法。因为字符串是明文,可能会被恶意攻击者窃取,从而破坏密钥的机密性。因此,在生产环境中,我们应该使用更安全的方法来生成密钥,比如使用随机数生成器。
相关问题
c语言生成128bit的素数
生成128位素数的一种常见方法是使用Miller-Rabin素性测试。以下是一个示例程序:
```c
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <stdbool.h>
#include <stdint.h>
#define MAX_ITERATIONS 64
// 128位正整数结构体
typedef struct {
uint64_t high;
uint64_t low;
} uint128_t;
// 将字符串转换为128位正整数
void str_to_uint128(char* str, uint128_t* num) {
int len = strlen(str);
num->high = 0;
num->low = 0;
for (int i = 0; i < len; i++) {
num->low = num->low * 10 + (str[i] - '0');
num->high += num->low / 10000000000000000000ULL;
num->low %= 10000000000000000000ULL;
}
}
// 将128位正整数转换为字符串
void uint128_to_str(uint128_t num, char* str) {
uint64_t tmp;
int len = 0;
while (num.high > 0) {
tmp = num.high % 10;
str[len++] = '0' + tmp;
num.high /= 10;
}
while (num.low > 0) {
tmp = num.low % 10;
str[len++] = '0' + tmp;
num.low /= 10;
}
if (len == 0) {
str[len++] = '0';
}
str[len] = '\0';
for (int i = 0; i < len / 2; i++) {
char tmp = str[i];
str[i] = str[len - i - 1];
str[len - i - 1] = tmp;
}
}
// 128位正整数加法
uint128_t uint128_add(uint128_t a, uint128_t b) {
uint128_t res;
res.high = a.high + b.high;
res.low = a.low + b.low;
if (res.low < a.low) {
res.high++;
}
return res;
}
// 128位正整数减法
uint128_t uint128_sub(uint128_t a, uint128_t b) {
uint128_t res;
res.high = a.high - b.high;
res.low = a.low - b.low;
if (res.low > a.low) {
res.high--;
}
return res;
}
// 128位正整数乘法
uint128_t uint128_mul(uint128_t a, uint128_t b) {
uint128_t res;
uint64_t a_high = a.high;
uint64_t a_low = a.low;
uint64_t b_high = b.high;
uint64_t b_low = b.low;
res.low = a_low * b_low;
res.high = a_high * b_low + a_low * b_high + (res.low / 10000000000000000000ULL);
res.low %= 10000000000000000000ULL;
res.high += a_high * b_high;
return res;
}
// 128位正整数除以2
uint128_t uint128_div2(uint128_t a) {
uint128_t res;
res.high = a.high >> 1;
res.low = (a.high & 1) * 1000000000000000000ULL + (a.low >> 1);
return res;
}
// 128位正整数取模
uint128_t uint128_mod(uint128_t a, uint128_t b) {
while (a.high > 0 || a.low >= b.low) {
if (a.high < b.high || (a.high == b.high && a.low < b.low)) {
break;
}
uint128_t tmp = b;
uint128_t mul = { 1, 0 };
while (tmp.high < a.high || (tmp.high == a.high && tmp.low <= a.low)) {
tmp = uint128_add(tmp, tmp);
mul = uint128_add(mul, mul);
}
a = uint128_sub(a, tmp);
b = uint128_sub(b, mul);
}
return a;
}
// 128位正整数幂取模
uint128_t uint128_powmod(uint128_t a, uint128_t b, uint128_t mod) {
uint128_t res = { 1, 0 };
while (b.high > 0 || b.low > 0) {
if (b.low & 1) {
res = uint128_mod(uint128_mul(res, a), mod);
}
a = uint128_mod(uint128_mul(a, a), mod);
b = uint128_div2(b);
}
return res;
}
// Miller-Rabin素性测试
bool miller_rabin_test(uint128_t n) {
if (n.high == 0 && n.low < 2) {
return false;
}
if (n.low == 2) {
return true;
}
if ((n.low & 1) == 0) {
return false;
}
uint128_t d = uint128_sub(n, (uint128_t){ 1, 0 });
while ((d.low & 1) == 0) {
d = uint128_div2(d);
}
for (int i = 0; i < MAX_ITERATIONS; i++) {
uint128_t a;
do {
a.high = rand() | ((uint64_t)rand() << 32);
a.low = rand() | ((uint64_t)rand() << 32);
} while (a.high == 0 && a.low == 0);
uint128_t x = uint128_powmod(a, d, n);
if (x.high == 0 && x.low == 1) {
continue;
}
bool probable_prime = false;
while (d.high > 0 || d.low > 0) {
x = uint128_mod(uint128_mul(x, x), n);
d = uint128_div2(d);
if (x.high == 0 && x.low == 1) {
probable_prime = true;
break;
}
if (x.high == 0 && x.low == n.low - 1) {
probable_prime = true;
break;
}
}
if (!probable_prime) {
return false;
}
}
return true;
}
// 生成随机128位正整数
void random_uint128(uint128_t* num) {
num->high = rand() | ((uint64_t)rand() << 32);
num->low = rand() | ((uint64_t)rand() << 32);
}
// 生成128位素数
void generate_prime(uint128_t* num) {
do {
random_uint128(num);
num->low |= 1;
} while (!miller_rabin_test(*num));
}
int main() {
srand((unsigned)time(NULL));
uint128_t num;
generate_prime(&num);
char str[40];
uint128_to_str(num, str);
printf("%s\n", str);
return 0;
}
```
注意:此程序仅供参考,实际应用中应该考虑更多的安全性和效率问题。
使用java写一个randomkey的子类实现生成128bit随机密钥
可以创建一个`RandomKey`类来实现生成128位随机密钥的功能,代码如下:
```
import java.security.SecureRandom;
public class RandomKey extends Object {
private static final int DEFAULT_KEY_SIZE = 128; // 默认密钥长度为128位
private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
private int size; // 密钥长度
public RandomKey(int size) {
this.size = size;
}
public RandomKey() {
this(DEFAULT_KEY_SIZE);
}
public byte[] generateKeyBytes() {
SecureRandom random = new SecureRandom();
byte[] key = new byte[size / 8];
random.nextBytes(key);
return key;
}
public String generateKey() {
return bytesToHex(generateKeyBytes());
}
private String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for (int i = 0; i < bytes.length; i++) {
int v = bytes[i] & 0xFF;
hexChars[i * 2] = HEX_ARRAY[v >>> 4];
hexChars[i * 2 + 1] = HEX_ARRAY[v & 0x0F];
}
return new String(hexChars);
}
}
```
这个类有两个构造器,一个是带参数的构造器,用于指定密钥长度;另一个是默认构造器,使用默认的密钥长度128位。`generateKeyBytes()`方法生成一个随机字节数组,`generateKey()`方法将这个字节数组转换为16进制字符串,作为随机密钥返回。
你可以像下面这样使用这个类:
```
RandomKey randomKey = new RandomKey();
String key = randomKey.generateKey();
System.out.println("随机密钥:" + key);
```
这个程序会输出一个随机生成的128位随机密钥,例如:
```
随机密钥:B7C5B3E2C8A7C60E9B8D8A7E4A5C0A1F
```