在Objective-c中用字节为单位的模和指数生成RSA公钥

Question

我搜索了许多网站，试图了解RSA是如何工作的。

我有一个模数“856C2F888474B83612A82E4E00D0CD4069A6783140433D50725F”和指数“03”，我必须解密以十六进制字节组成的信息。我的问题是：

如何创建公钥？一旦我有了公钥，我必须在base64中编码还是公钥准备解密？

Answer 1

经过几天的研究，我终于用OpenSSL完成了。我不是C++方面的专家，所以我不确定是否所有的字符、常量字符和无符号字符都声明正确，所以如果有人有更好的想法，请编辑它=)。你必须有lybcrypto.a和libssl.a（在这里你可以找到它们https://github.com/x2on/openssl-for-iphone）。我用EMV VISA密钥测试了几次，它有效。

#include <openssl/opensslv.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/bn.h>

@implementation ViewController

-(NSData*) decryptIPKC:(NSString*)ipkc modulus:(NSString*)mod exponent:(NSString*)exp{

NSString * hexString = ipkc;
int hexStringLength= [hexString length] / 2;

//unsigned char enc_bin[144];
unsigned char dec_bin[hexStringLength];
//int enc_len;
int dec_len;
RSA * rsa_pub = RSA_new();


const char *N=[mod UTF8String] ;
const char *E=[exp UTF8String];



char * myBuffer = (char *)malloc((int)[hexString length] / 2 + 1);
bzero(myBuffer, [hexString length] / 2 + 1);
for (int i = 0; i < [hexString length] - 1; i += 2) {
unsigned int anInt;
NSString * hexCharStr = [hexString substringWithRange:NSMakeRange(i, 2)];
NSScanner * scanner = [[NSScanner alloc] initWithString:hexCharStr];
[scanner scanHexInt:&anInt];
myBuffer[i / 2] = (char)anInt;
}

printf("Mybuffer: %s",myBuffer);

if (!BN_hex2bn(&rsa_pub->n, N)) {
printf("NO CARGO EL MODULO");
}
printf(" N: %s\n", N);
printf(" n: %s\n", BN_bn2hex(rsa_pub->n));


if (!BN_hex2bn(&rsa_pub->e, E)) {
printf("NO  CARGO EL EXPONENTE");
}
printf(" E: %s\n", E);
printf(" e: %s\n", BN_bn2hex(rsa_pub->e));

printf("public key size : %d bits\n", RSA_size(rsa_pub));    

/* decrypt */
if ((dec_len = RSA_public_decrypt(hexStringLength, (unsigned char*)myBuffer, dec_bin, rsa_pub,RSA_NO_PADDING))<0) {
printf("NO\n ");
}
printf("decrypted data:\n %s", dec_bin);
print_hex(dec_bin, dec_len);

NSData* data = [NSData dataWithBytes:dec_bin length:sizeof(dec_bin)];

free(myBuffer);

return data;
}
- (void)viewDidLoad {
[super viewDidLoad];
NSString *m= @"Your HEX modulus here";
NSString *e=@"Your HEX exponent";
NSString * hexString= @"Your HEX message here";

NSData *decryptedIPKC= [self decryptIPKC:hexString modulus:m exponent:e];
NSLog(@"ESTE ES EL NSDATA %@", decryptedIPKC.description);
}

@end