openssl 學習之從證書中提取RSA公鑰N 和 E

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原文鏈接:?http://blog.csdn.net/kkxgx/article/details/19850509

通常數字證書包含很多信息，其中N和E值即我們稱為的公鑰。如何從PEM 或者DER格式的證書中提出證書呢？下面給出代碼實現從PEM和DER編碼的證書中提出N、E。

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#include?<openssl/evp.h>??
#include?<openssl/x509.h>??
#include?<stdio.h>??
#include?<stdlib.h>??
void?PrintHex(unsigned?char?*str,?unsigned?int?len)??
{??
????int?i?=?0;??
????for(i?=0;i<?len;?i++)??
????{??
????????if(i%4?==?0)??
????{??
???????printf("0x");??
????}??
????????printf("%02x",str[i]);??
????if(i%4?==?3)??
????????{??
???????????printf("?");??
????????}??
????????if(i%16?==?15)??
????????{??
????????printf("\n");??
????????}??
????}??
????printf("\n");??
}??
void?GetPukfromPEM()??
{??
????X509?*x;??
????BIO?*b;??
????EVP_PKEY?*k;??
????RSA?*rsa;??
????unsigned?char?n[300]?={0x0};??
????unsigned?char?e[300]?={0x0};??
????unsigned?int?len;??
????/*www.google.com1為PEM格式的數字證書，從firefox中導出?*/???????
????b=BIO_new_file("www.google.com1","r");??
????x=PEM_read_bio_X509(b,NULL,NULL,NULL);??
????k=X509_get_pubkey(x);??
????rsa=EVP_PKEY_get1_RSA(k);??
????if(rsa->n?!=?NULL)??
????{??
????????BN_bn2bin(rsa->n,?n);??
????????len=?BN_num_bytes(rsa->n);??
????????printf("N:\n");??
????????PrintHex(n,len);??
????}??
????else??
????{??
????????printf("PEM?error?\n");??
????}??
????if(rsa->e?!=?NULL)??
????{??
????????BN_bn2bin(rsa->e,?e);??
????????len=?BN_num_bytes(rsa->e);????
????????printf("E:\n");??
????????PrintHex(e,len);??
????}??
????else??
????{??
????????printf("PEM?error?\n");??
????}??
????BIO_free(b);??
????X509_free(x);??
}??
void?GetPukfromDER()??
{??
????X509?*x;??
????FILE?*fp;??
????unsigned?char???buf[5000],*p;??
????int?ret;??
? ??
????EVP_PKEY?*k;??
????RSA?*rsa;??
????unsigned?char?n[300]?={0x0};??
????unsigned?char?e[300]?={0x0};??
????unsigned?int?len;??
????/*?www.google.com2為DER編碼的數字證書?，從firefox中導出?
????*/??
????fp=fopen("www.google.com2","rb");??
????if(!fp)?return?;??
????len=fread(buf,1,5000,fp);??
????fclose(fp);??
????p=buf;??
????x=X509_new();??
????d2i_X509(&x,(const?unsigned?char?**)&p,len);??
????k=X509_get_pubkey(x);??
????rsa=EVP_PKEY_get1_RSA(k);??
????if(rsa->n?!=?NULL)??
????{??
????????BN_bn2bin(rsa->n,?n);??
????????len=?BN_num_bytes(rsa->n);??
????printf("N:\n");??
????PrintHex(n,len);??
????}??
????else??
????{??
????????printf("DER?error?\n");??
????}??
????if(rsa->e?!=?NULL)??
????{??
????????BN_bn2bin(rsa->e,?e);??
????????len=?BN_num_bytes(rsa->e);??
????????printf("E:\n");??
????????PrintHex(e,len);??
????}??
????else??
????{??
????????printf("DER?error?\n");??
????}??
? ? ??
????X509_free(x);?????
}??
int?main()??
{??
????GetPukfromPEM();??
????GetPukfromDER();??
????return?0;??
}??

程序執行結果如下：

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N:??
0xb073f0f2?0x04eec2a2?0x46ca342a?0xaabb6023???
0xd111761f?0x1f3ad065?0x834e9a45?0xa8437085???
0x76f01f87?0x00021f6e?0x3b1717c4?0xb5e91946???
0xa292258d?0x622ab463?0x301fb985?0xf835e116???
0x5a7649cc?0x50485339?0x5989d684?0x02fb9aec???
0x1bc751d5?0x769590d4?0x3a2ab8a6?0xde024d06???
0xfbcdeda5?0x46415f55?0x74e5ec7e?0x40dc509c???
0xb5e4355d?0x1e6820f8?0xe9dea36a?0x28bf41d2???
0xa1b3e225?0x8d0c1bca?0x3d930c18?0xaedfc5bc???
0xfdbc82ba?0x6800d716?0x32719f65?0xb511da68???
0x59d0a657?0x641bc9fe?0x98e5f5a5?0x65eae1db???
0xeef4b39d?0xb38eea87?0xae16d21e?0xa07c7c69???
0x3f291685?0x0153a76c?0xf160abdd?0xa2fc2547???
0xd432d112?0xddf74812?0xe0fc9ca2?0x7798e989???
0x99b8f838?0xf18c06c2?0x7a23366d?0x9b9dcd30???
0xc8c73417?0x1ebb7d42?0xc8abe715?0x16f673b5???
??
E:??
0x010001??
N:??
0xb073f0f2?0x04eec2a2?0x46ca342a?0xaabb6023???
0xd111761f?0x1f3ad065?0x834e9a45?0xa8437085???
0x76f01f87?0x00021f6e?0x3b1717c4?0xb5e91946???
0xa292258d?0x622ab463?0x301fb985?0xf835e116???
0x5a7649cc?0x50485339?0x5989d684?0x02fb9aec???
0x1bc751d5?0x769590d4?0x3a2ab8a6?0xde024d06???
0xfbcdeda5?0x46415f55?0x74e5ec7e?0x40dc509c???
0xb5e4355d?0x1e6820f8?0xe9dea36a?0x28bf41d2???
0xa1b3e225?0x8d0c1bca?0x3d930c18?0xaedfc5bc???
0xfdbc82ba?0x6800d716?0x32719f65?0xb511da68???
0x59d0a657?0x641bc9fe?0x98e5f5a5?0x65eae1db???
0xeef4b39d?0xb38eea87?0xae16d21e?0xa07c7c69???
0x3f291685?0x0153a76c?0xf160abdd?0xa2fc2547???
0xd432d112?0xddf74812?0xe0fc9ca2?0x7798e989???
0x99b8f838?0xf18c06c2?0x7a23366d?0x9b9dcd30???
0xc8c73417?0x1ebb7d42?0xc8abe715?0x16f673b5???
??
E:??
0x010001 ?

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