我有两个密钥,公共和私有,都存储在SecKeyRef变量中.为了简单起见,让我们从公众开始.我想做的是将其导出为NSData对象.为此,苹果提供了几个着名的代码片段,它们在这里：
- (NSData *)getPublicKeyBits {
OSStatus sanityCheck = noErr;
NSData * publicKeyBits = nil;
NSMutableDictionary * queryPublicKey = [[NSMutableDictionary alloc] init];
// Set the public key query dictionary.
[queryPublicKey setObject:(id)kSecClassKey forKey:(id)kSecClass];
[queryPublicKey setObject:publicTag forKey:(id)kSecAttrApplicationTag];
[queryPublicKey setObject:(id)kSecAttrKeyTypeRSA forKey:(id)kSecAttrKeyType];
[queryPublicKey setObject:[NSNumber numberWithBool:YES] forKey:(id)kSecReturnData];
// Get the key bits.
sanityCheck = SecItemCopyMatching((CFDictionaryRef)queryPublicKey,(CFTypeRef *)&publicKeyBits);
if (sanityCheck != noErr)
{
publicKeyBits = nil;
}
[queryPublicKey release];
return publicKeyBits;
}
我有Xcode 4.6.2,但代码显示错误(“__bridge”在每次转换到id之前被添加).新版本如下所示：
- (NSData *)getPublicKeyBitsFromKey:(SecKeyRef)givenKey {
OSStatus sanityCheck = noErr;
NSData * publicKeyBits = nil;
NSMutableDictionary * queryPublicKey = [[NSMutableDictionary alloc] init];
// Set the public key query dictionary.
[queryPublicKey setObject:(__bridge id)kSecClassKey forKey:(__bridge id)kSecClass];
[queryPublicKey setObject:publicTag forKey:(__bridge id)kSecAttrApplicationTag];
[queryPublicKey setObject:(__bridge id)kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
[queryPublicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnData];
// Get the key bits.
sanityCheck = SecItemCopyMatching((__bridge CFDictionaryRef)queryPublicKey,(CFTypeRef *)&publicKeyBits);
if (sanityCheck != noErr)
{
publicKeyBits = nil;
}
return publicKeyBits;
}
但是还有两个错误：
>使用未声明的标识符’publicTag’
>对于指向“CFTypeRef”(也称为“const void *”)的Objective-C指针的间接指针的转换不允许使用ARC
现在,我希望在您的帮助之后,第一个问题将不再是一个问题,因为我不想构建一个查询或什么不能从钥匙串中提取密钥.我有一个变量,我想从中提取它.该变量的名称为givenPublicKey,这是我要转换为NSData的关键字.
那么,我怎么去做这个和解决这个ARC问题？
后续程序：如何将私钥导出到NSData,因为我已经读了几次,我正在尝试使用的功能只适用于公钥.
解决方法
>使用未声明的标识符’publicTag’
publicTag只是添加到Keychain项目中的一些唯一标识符.在CryptoExercise示例项目中,它定义为
#define kPublicKeyTag "com.apple.sample.publickey" static const uint8_t publicKeyIdentifier[] = kPublicKeyTag; NSData *publicTag = [[NSData alloc] initWithBytes:publicKeyIdentifier length:sizeof(publicKeyIdentifier)];
>对于指向“CFTypeRef”(也称为“const void *”)的Objective-C指针的间接指针的转换不允许使用ARC
这可以通过使用临时CFTypeRef变量来解决：
CFTypeRef result;
sanityCheck = SecItemCopyMatching((__bridge CFDictionaryRef)queryPublicKey,&result);
if (sanityCheck == errSecSuccess) {
publicKeyBits = CFBridgingRelease(result);
}
>我不想构建一个查询,或者什么不能从钥匙串中提取密钥.我有一个变量,我想从中提取它
据我所知,您必须临时将密钥匙存储到钥匙扣. SecItemAdd
可以选择将添加的项目作为数据返回.从文档：
To obtain the data of the added item as an object of type
CFDataRef,
specify the return type keykSecReturnDatawith a value of
kcfBooleanTrue.
把所有的一切,以下代码应该做你想要的：
- (NSData *)getPublicKeyBitsFromKey:(SecKeyRef)givenKey {
static const uint8_t publicKeyIdentifier[] = "com.your.company.publickey";
NSData *publicTag = [[NSData alloc] initWithBytes:publicKeyIdentifier length:sizeof(publicKeyIdentifier)];
OSStatus sanityCheck = noErr;
NSData * publicKeyBits = nil;
NSMutableDictionary * queryPublicKey = [[NSMutableDictionary alloc] init];
[queryPublicKey setObject:(__bridge id)kSecClassKey forKey:(__bridge id)kSecClass];
[queryPublicKey setObject:publicTag forKey:(__bridge id)kSecAttrApplicationTag];
[queryPublicKey setObject:(__bridge id)kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
// Temporarily add key to the Keychain,return as data:
NSMutableDictionary * attributes = [queryPublicKey mutableCopy];
[attributes setObject:(__bridge id)givenKey forKey:(__bridge id)kSecValueRef];
[attributes setObject:@YES forKey:(__bridge id)kSecReturnData];
CFTypeRef result;
sanityCheck = SecItemAdd((__bridge CFDictionaryRef) attributes,&result);
if (sanityCheck == errSecSuccess) {
publicKeyBits = CFBridgingRelease(result);
// Remove from Keychain again:
(void)SecItemDelete((__bridge CFDictionaryRef) queryPublicKey);
}
return publicKeyBits;
}
我希望这样工作,我现在不能测试.
>跟进：如何将私钥导出到NSData,因为我已经读了好几次,我正在尝试使用的功能只适用于公钥.
我不知道.
