如何找出iPhone / Objective C上RSA公钥的模数和指数 [英] How to find out the modulus and exponent of RSA Public Key on iPhone/Objective C

问题描述

解决方案

有没有办法找出使用SecKeyGeneratePair（安全框架）创建的公钥的模数和指数？ / div>

打破了我的头，但这里是一个解决方案，我发现（不使用任何外部包）。

首先，去苹果的CryptoExercise示例。从那里下载SecKeyWrapper类。该类中有趣的功能是getPublicKeyBits。

链接到示例： http://developer.apple.com/library/ios/#samplecode/CryptoExercise/Introduction/Intro.html

您将收到的位是包含模数和exp的DER编码（wiki it）公钥。这里有一个代码可以为您解码，很简单：

   - （NSData *）getPublicKeyExp 
 {
 NSData * pk = [self getPublicKeyBits]; 
 if（pk == NULL）return NULL; 
 
 int iterator = 0; 
 
迭代器++; // TYPE  -  bit stream  -  mod + exp 
 [self derEncodingGetSizeFrom：pk at：& iterator]; //总大小
 
 iterator ++; // TYPE  -  bit stream mod 
 int mod_size = [self derEncodingGetSizeFrom：pk at：& iterator]; 
 iterator + = mod_size; 
 
迭代器++; // TYPE  -  bit stream exp 
 int exp_size = [self derEncodingGetSizeFrom：pk at：& iterator]; 
 
 return [pk subdataWithRange：NSMakeRange（iterator，exp_size）]; 
} 
 
  - （NSData *）getPublicKeyMod 
 {
 NSData * pk = [self getPublicKeyBits]; 
 if（pk == NULL）return NULL; 
 
 int iterator = 0; 
 
迭代器++; // TYPE  -  bit stream  -  mod + exp 
 [self derEncodingGetSizeFrom：pk at：& iterator]; //总大小
 
 iterator ++; // TYPE  -  bit stream mod 
 int mod_size = [self derEncodingGetSizeFrom：pk at：& iterator]; 
 
 return [pk subdataWithRange：NSMakeRange（iterator，mod_size）]; 
} 
 
  - （int）derEncodingGetSizeFrom：（NSData *）buf at：（int *）iterator 
 {
 const uint8_t * data = [buf bytes]; 
 int itr = * iterator; 
 int num_bytes = 1; 
 int ret = 0; 
 
 if（data [itr]> 0x80）{
 num_bytes = data [itr]  -  0x80; 
 itr ++; （int i = 0; i< num_bytes; i ++）ret =（ret * 0x100）+ data [itr + i]; 
} 
 
 
 
 * iterator = itr + num_bytes; 
 return ret; 
} 
  

Is there a possible way to find out the modulus and exponent of the Public Key, created with SecKeyGeneratePair (the Security Framework in general)?

解决方案

Busted my head on this, but here's a solution I've found (without using any external packages).

First, go to Apple's CryptoExercise example. Download the "SecKeyWrapper" class from there. The interesting function in that class is getPublicKeyBits.

Link to the example: http://developer.apple.com/library/ios/#samplecode/CryptoExercise/Introduction/Intro.html

The bits you will receive is a DER encoded (wiki it) public key containing both the modulus and exp. Here's a code that will decode it for you, pretty easy:

- (NSData *)getPublicKeyExp
{
    NSData* pk = [self getPublicKeyBits];
    if (pk == NULL) return NULL;

    int iterator = 0;

    iterator++; // TYPE - bit stream - mod + exp
    [self derEncodingGetSizeFrom:pk at:&iterator]; // Total size

    iterator++; // TYPE - bit stream mod
    int mod_size = [self derEncodingGetSizeFrom:pk at:&iterator];
    iterator += mod_size;

    iterator++; // TYPE - bit stream exp
    int exp_size = [self derEncodingGetSizeFrom:pk at:&iterator];

    return [pk subdataWithRange:NSMakeRange(iterator, exp_size)];
}

- (NSData *)getPublicKeyMod
{
    NSData* pk = [self getPublicKeyBits];
    if (pk == NULL) return NULL;

    int iterator = 0;

    iterator++; // TYPE - bit stream - mod + exp
    [self derEncodingGetSizeFrom:pk at:&iterator]; // Total size

    iterator++; // TYPE - bit stream mod
    int mod_size = [self derEncodingGetSizeFrom:pk at:&iterator];

    return [pk subdataWithRange:NSMakeRange(iterator, mod_size)];
}

- (int)derEncodingGetSizeFrom:(NSData*)buf at:(int*)iterator
{
    const uint8_t* data = [buf bytes];
    int itr = *iterator;
    int num_bytes = 1;
    int ret = 0;

    if (data[itr] > 0x80) {
        num_bytes = data[itr] - 0x80;
        itr++;
    }

    for (int i = 0 ; i < num_bytes; i++) ret = (ret * 0x100) + data[itr + i];

    *iterator = itr + num_bytes;
    return ret;
}

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