英文:
compute the remainder of the BIGNUM divided by any integer modulo
问题
这是您提供的代码的翻译：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/bn.h>
int main() {
unsigned char message[] = "hello world"; // 消息
// hello world = 01101000 01100101 01101100 01101100 01101111 00100000 01110111 01101111 01110010 01101100 01100100
// 位的值为 126207244316550804821666916
int length = strlen((char *)message);
int i, j;
BIGNUM *bn = BN_new();
BN_zero(bn);
for (i = 0; i < length; i++) {
for (j = 0; j < 8; j++) {
if (message[i] >> (7 - j) & 1) {
BN_lshift(bn, bn, 1);
BN_add_word(bn, 1);
} else {
BN_lshift(bn, bn, 1);
}
}
}
BIGNUM *modulus = BN_new();
BN_set_word(modulus, 1024);
BN_mod(bn, bn, modulus, NULL);
char *dec = BN_bn2dec(bn);
printf("%s\n", dec);
OPENSSL_free(dec);
BN_free(bn);
BN_free(modulus);
return 0;
}
这段代码的目标是将字符串"hello world"转换为位并计算其模1024的余数。您提供的代码似乎有一些错误，导致出现Segmentation Fault错误。如果需要进一步的调试和修复，请提供更多上下文或相关错误信息。
英文:
given some string, let assume , hello world. I know that the string in bits is: 01101000 01100101 01101100 01101100 01101111 00100000 01110111 01101111 01110010 01101100 01100100. so the value of the bits is 126207244316550804821666916. I was able to create code that give my the value of the bits. now I want to compute the remainder of the BIGNUM divided by any integer modulus, let assume 1024. I expect to get number between 0 to 1023. but when i trying to apply the modulo , i get error: Segmentation fault (core dumped)
this is the code that I using:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/bn.h>
int main() {
unsigned char message[] = "hello world"; //message
//hello world = 01101000 01100101 01101100 01101100 01101111 00100000 01110111 01101111 01110010 01101100 01100100
//the value of bits is 126207244316550804821666916
int length = strlen((char *)message);
int i,j;
BIGNUM *bn = BN_new();
BN_zero(bn);
for (i = 0; i < length; i++) {
for(int j=0; j<8; j++){
if (message[i] >> (7-j) & 1) {
BN_lshift(bn, bn, 1);
BN_add_word(bn, 1);
}
else {
BN_lshift(bn, bn, 1);
}
}
}
BIGNUM *modolus = BN_new();
BN_set_word(modolus, 1024);
BN_mod(bn, bn, modolus, NULL);
char *dec = BN_bn2dec(bn);
printf("%s\n", dec);
OPENSSL_free(dec);
BN_free(bn);
BN_free(modolus);
return 0;
}
I'm new to C, i not sure what is exactly wrong here. after the loop i expect to get in bn the value 126207244316550804821666916, and its seems right. but when make module with 1024, i got error.
答案1
得分: 2
你不能将空指针用作上下文参数。它需要指向有效的 BN_CTX 对象的指针。
例如，
BN_CTX *ctx = BN_CTX_new();
BN_mod(bn, bn, modolus, ctx);
BN_CTX_free(ctx);
在实际代码中，你会希望提前分配上下文对象并在后续计算中重复使用它，而不是立即释放它，当然。
英文:
You can't pass a null pointer as the context argument. It needs a pointer to a valid BN_CTX object.
For example,
BN_CTX *ctx = BN_CTX_new();
BN_mod(bn, bn, modolus, ctx);
BN_CTX_free(ctx);
In real code you'll want to allocate the context object ahead of time and re-use it for subsequent computations instead of freeing it right away, of course.
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