RSA加密(2.0)

参考http://blog.iamzsx.me/show.html?id=155002

针对于RSA加密，iOS端没有专门的支持RSA加密的接口（API）,所以一般有俩种解决RSA加密的方案

一，通过制作自签名的x509证书，再调用x509的相关API进行加密

二，通过制作通用的pem的密钥结合openssl静态库进行RSA加密

在上一篇文章RSA加密(1.0)我们已经提到制作证书的过程，其中private_key.pem是私钥，public_key.der是用于iOS的公钥

下面讲一下x509加密

上篇文章我们制作了适用于iOS的公钥public_key.der与私钥private_key.p12，此处会用到这俩个密钥，创建一个工程，将俩个密钥引入到工程中。并导入Security.framework

#import <Foundation/Foundation.h>

#import <Security/Security.h>

@interface RSA : NSObject{

    SecKeyRef publicKey;

    SecCertificateRef certificate;

    SecPolicyRef policy;

    SecTrustRef trust;

    size_t maxPlainLen;

}

- (NSData *)encryptWithData:(NSData *)content;

- (NSData *)encryptWithSting:(NSString *)content;

@end

#import "RSA.h"

#import <Security/Security.h>

@implementation RSA

- (id)init{

    if (self = [super init]) {

        NSString *public_keyPath = [[NSBundle mainBundle] pathForResource:@"public_key" ofType:@"der"];

        if (public_keyPath == nil) {

            NSLog(@"没有发现公钥");

            return nil;

        }

        NSData *publicKeyFileContent = [NSData dataWithContentsOfFile:public_keyPath];

        if (publicKeyFileContent == nil) {

            NSLog(@"不能读取公钥内容");

            return nil;

        }

        certificate = SecCertificateCreateWithData(kCFAllocatorDefault, (__bridge CFDataRef)publicKeyFileContent);

        if (certificate == nil) {

            NSLog(@"不能读到证书");

            return nil;

        }

        policy = SecPolicyCreateBasicX509();

        OSStatus returnCode = SecTrustCreateWithCertificates(certificate, policy, &trust);

        if (returnCode != 0) {

            NSLog(@"SecTrustCreateWithCertificates失败.Error Code:%d",(int)returnCode);

            return nil;

        }

        SecTrustResultType trustResultType;

        returnCode = SecTrustEvaluate(trust, &trustResultType);

        if (returnCode != 0) {

            NSLog(@"SecTrustEvaluate失败.Error Code:%d",(int)returnCode);

            return nil;

        }

        publicKey = SecTrustCopyPublicKey(trust);

        if (publicKey == nil) {

            NSLog(@"SecTrustCopyPublicKey fail");

            return nil;

        }

        maxPlainLen = SecKeyGetBlockSize(publicKey)-12;

    }

    return self;

}

- (NSData *)encryptWithData:(NSData *)content{

    size_t plainLen = [content length];

    if (plainLen > maxPlainLen) {

        NSLog(@"加密内容（%ld）太长,加密内容必须小于%ld",plainLen,maxPlainLen);

        return nil;

    }

    void *plain = malloc(plainLen);

    [content getBytes:plain length:plainLen];

    size_t cipherLen = 128;//当前密钥长度是128字节

    void *cipher = malloc(cipherLen);

    OSStatus returnCode = SecKeyEncrypt(publicKey,kSecPaddingPKCS1, plain,plainLen, cipher, &cipherLen);

    NSData *result = nil;

    if (returnCode != 0) {

        NSLog(@"SecKeyEncrypt失败.Error code:%d",(int)returnCode);

    }else{

        result = [NSData dataWithBytes:cipher length:cipherLen];

    }

    free(plain);

    free(cipher);

    return result;

}

- (NSData *)encryptWithSting:(NSString *)content{

    return [self encryptWithData:[content dataUsingEncoding:NSUTF8StringEncoding]];

}

- (void)dealloc{

    CFRelease(certificate);

    CFRelease(trust);

    CFRelease(policy);

    CFRelease(publicKey);

}

 

@end

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