t-digest是什么算法
时间: 2024-01-25 21:51:38 浏览: 147
t-digest是一种用于高效计算数据分位数的算法。它可以在不需要存储所有数据的情况下,快速地计算出给定数据集中任意分位数的值。t-digest算法通过将数据分为多个小区间,并对每个小区间中的值进行统计和合并,来实现高效的分位数计算。这使得t-digest算法可以应用于大规模的数据集,同时保持较高的准确性。t-digest算法在大数据处理、机器学习、数据挖掘等领域有着广泛的应用。
相关问题
使用c++实现SHA-1算法
SHA-1是一种加密哈希算法,它将任意长度的消息压缩为一个160位的消息摘要。下面是使用C++实现SHA-1算法的示例代码:
```c++
#include <iostream>
#include <cstring>
#include <cstdint>
// 循环左移函数
#define ROTLEFT(a,b) ((a << b) | (a >> (32-b)))
// 定义常量K
const uint32_t K[] = {
0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6
};
// SHA-1算法函数
void sha1(uint8_t* message, uint32_t message_length, uint32_t* digest) {
// 初始化缓冲区
uint32_t H[] = {
0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0
};
// 计算填充位数
uint32_t padding_length = 64 - ((message_length + 8) % 64);
// 填充消息
uint8_t* padded_message = new uint8_t[message_length + padding_length + 8];
std::memcpy(padded_message, message, message_length);
padded_message[message_length] = 0x80;
std::memset(padded_message + message_length + 1, 0, padding_length - 1);
// 将消息长度添加到消息末尾
uint64_t message_bit_length = message_length * 8;
std::memcpy(padded_message + message_length + padding_length, &message_bit_length, sizeof(message_bit_length));
// 处理每个512位的分组
for (uint32_t i = 0; i < message_length + padding_length + 8; i += 64) {
// 将分组划分为16个32位的字
uint32_t* w = new uint32_t[80];
for (uint32_t j = 0; j < 16; j++) {
w[j] = (padded_message[i + j * 4] << 24) |
(padded_message[i + j * 4 + 1] << 16) |
(padded_message[i + j * 4 + 2] << 8) |
(padded_message[i + j * 4 + 3]);
}
// 扩展16个字为80个字
for (uint32_t j = 16; j < 80; j++) {
w[j] = ROTLEFT(w[j-3] ^ w[j-8] ^ w[j-14] ^ w[j-16], 1);
}
// 初始化哈希值
uint32_t a = H[0];
uint32_t b = H[1];
uint32_t c = H[2];
uint32_t d = H[3];
uint32_t e = H[4];
// 主循环
for (uint32_t j = 0; j < 80; j++) {
uint32_t f, k;
if (j < 20) {
f = (b & c) | ((~b) & d);
k = K[0];
} else if (j < 40) {
f = b ^ c ^ d;
k = K[1];
} else if (j < 60) {
f = (b & c) | (b & d) | (c & d);
k = K[2];
} else {
f = b ^ c ^ d;
k = K[3];
}
uint32_t temp = ROTLEFT(a, 5) + f + e + k + w[j];
e = d;
d = c;
c = ROTLEFT(b, 30);
b = a;
a = temp;
}
// 更新哈希值
H[0] += a;
H[1] += b;
H[2] += c;
H[3] += d;
H[4] += e;
// 释放内存
delete[] w;
}
// 保存哈希值
std::memcpy(digest, H, sizeof(H));
// 释放内存
delete[] padded_message;
}
int main() {
uint8_t message[] = "hello world";
uint32_t digest[5];
sha1(message, std::strlen((const char*)message), digest);
std::cout << std::hex << digest[0] << digest[1] << digest[2] << digest[3] << digest[4] << std::endl;
return 0;
}
```
注意,这只是一个简单的示例代码,实际应用中需要考虑更多安全性和性能方面的问题。
sha-1算法的c语言实现
以下是SHA-1算法的C语言实现,包含了初始化、填充、转换和输出四个步骤:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#define SHA1_BLOCK_SIZE 20
// SHA-1 functions
#define SHA1_ROTLEFT(a,b) (((a) << (b)) | ((a) >> (32-(b))))
#define SHA1_ROTRIGHT(a,b) (((a) >> (b)) | ((a) << (32-(b))))
#define SHA1_CH(x,y,z) (((x) & (y)) ^ (~(x) & (z)))
#define SHA1_MAJ(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
#define SHA1_E0(x) (SHA1_ROTRIGHT(x, 2) ^ SHA1_ROTRIGHT(x, 13) ^ SHA1_ROTRIGHT(x, 22))
#define SHA1_E1(x) (SHA1_ROTRIGHT(x, 6) ^ SHA1_ROTRIGHT(x, 11) ^ SHA1_ROTRIGHT(x, 25))
#define SHA1_F0(x) (SHA1_ROTRIGHT(x, 7) ^ SHA1_ROTRIGHT(x, 18) ^ ((x) >> 3))
#define SHA1_F1(x) (SHA1_ROTRIGHT(x, 17) ^ SHA1_ROTRIGHT(x, 19) ^ ((x) >> 10))
void sha1_transform(uint32_t *state, const uint8_t *buffer) {
uint32_t a, b, c, d, e, temp;
uint32_t w[80];
int i;
// Copy buffer to work array
for (i = 0; i < 16; i++) {
w[i] = ((uint32_t)buffer[i * 4]) << 24;
w[i] |= ((uint32_t)buffer[i * 4 + 1]) << 16;
w[i] |= ((uint32_t)buffer[i * 4 + 2]) << 8;
w[i] |= ((uint32_t)buffer[i * 4 + 3]);
}
for (i = 16; i < 80; i++) {
w[i] = SHA1_ROTLEFT(w[i-3] ^ w[i-8] ^ w[i-14] ^ w[i-16], 1);
}
a = state[0];
b = state[1];
c = state[2];
d = state[3];
e = state[4];
for (i = 0; i < 20; i++) {
temp = SHA1_ROTLEFT(a, 5) + SHA1_CH(b, c, d) + e + w[i] + 0x5a827999;
e = d;
d = c;
c = SHA1_ROTLEFT(b, 30);
b = a;
a = temp;
}
for (i = 20; i < 40; i++) {
temp = SHA1_ROTLEFT(a, 5) + SHA1_MAJ(b, c, d) + e + w[i] + 0x6ed9eba1;
e = d;
d = c;
c = SHA1_ROTLEFT(b, 30);
b = a;
a = temp;
}
for (i = 40; i < 60; i++) {
temp = SHA1_ROTLEFT(a, 5) + SHA1_CH(b, c, d) + e + w[i] + 0x8f1bbcdc;
e = d;
d = c;
c = SHA1_ROTLEFT(b, 30);
b = a;
a = temp;
}
for (i = 60; i < 80; i++) {
temp = SHA1_ROTLEFT(a, 5) + SHA1_MAJ(b, c, d) + e + w[i] + 0xca62c1d6;
e = d;
d = c;
c = SHA1_ROTLEFT(b, 30);
b = a;
a = temp;
}
state[0] += a;
state[1] += b;
state[2] += c;
state[3] += d;
state[4] += e;
}
void sha1_init(uint32_t *state) {
state[0] = 0x67452301;
state[1] = 0xefcdab89;
state[2] = 0x98badcfe;
state[3] = 0x10325476;
state[4] = 0xc3d2e1f0;
}
void sha1_pad(uint8_t *buffer, int len) {
int i;
buffer[len] = 0x80;
for (i = len + 1; i % 64 != 56; i++) {
buffer[i] = 0x00;
}
len *= 8;
buffer[i++] = (len >> 56) & 0xff;
buffer[i++] = (len >> 48) & 0xff;
buffer[i++] = (len >> 40) & 0xff;
buffer[i++] = (len >> 32) & 0xff;
buffer[i++] = (len >> 24) & 0xff;
buffer[i++] = (len >> 16) & 0xff;
buffer[i++] = (len >> 8) & 0xff;
buffer[i++] = len & 0xff;
}
void sha1_digest(const uint32_t *state, uint8_t *hash) {
int i;
for (i = 0; i < 5; i++) {
hash[i * 4] = (state[i] >> 24) & 0xff;
hash[i * 4 + 1] = (state[i] >> 16) & 0xff;
hash[i * 4 + 2] = (state[i] >> 8) & 0xff;
hash[i * 4 + 3] = state[i] & 0xff;
}
}
void sha1(const uint8_t *data, int len, uint8_t *hash) {
uint32_t state[5];
uint8_t buffer[64];
int i;
sha1_init(state);
for (i = 0; i < len / 64; i++) {
memcpy(buffer, data + i * 64, 64);
sha1_transform(state, buffer);
}
memcpy(buffer, data + i * 64, len % 64);
sha1_pad(buffer, len % 64);
sha1_transform(state, buffer);
sha1_digest(state, hash);
}
int main() {
uint8_t data[] = "hello world";
uint8_t hash[SHA1_BLOCK_SIZE];
sha1(data, strlen((char*)data), hash);
printf("SHA1 hash of \"%s\": ", data);
for (int i = 0; i < SHA1_BLOCK_SIZE; i++) {
printf("%02x", hash[i]);
}
printf("\n");
return 0;
}
```
在这个实现中,`sha1()`函数接受一个输入数据和长度,以及一个输出缓冲区,将计算出的SHA-1摘要存储在缓冲区中。主函数演示了如何使用该函数计算数据的SHA-1摘要。