RSACryptographic, a set of RSA encryption/decryption for iOS/Mac OS

RSACryptographic.h

#import <Foundation/Foundation.h>

@interface RSACryptographic : NSObject

- (void)loadPublicKeyFromFile:(NSString*)derFilePath;
- (void)loadPublicKeyFromData:(NSData*)derData;

- (void)loadPrivateKeyFromFile:(NSString*)p12FilePath password:(NSString*)p12Password;
- (void)loadPrivateKeyFromData:(NSData*)p12Data password:(NSString*)p12Password;


- (NSString*)rsaEncryptString:(NSString*)string;
- (NSData*)rsaEncryptData:(NSData*)data ;

- (NSString*) rsaDecryptString:(NSString*)string;
- (NSData*)rsaDecryptData:(NSData*)data;

- (BOOL)rsaSHA1VerifyData:(NSData *)plainData
            withSignature:(NSData *)signature;

@end
  

RSACryptographic.m

#import "RSACryptographic.h"
#import <Security/Security.h>
#import <CommonCrypto/CommonCrypto.h>


@implementation RSACryptographic
{
    SecKeyRef publicKey;
    SecKeyRef privateKey;
}

- (void)dealloc {
    if (nil != publicKey) {
        CFRelease(publicKey);
    }
    if (nil != privateKey) {
        CFRelease(privateKey);
    }
}

- (SecKeyRef)getPublicKey {
    return publicKey;
}

- (SecKeyRef)getPrivateKey {
    return privateKey;
}

- (void)loadPublicKeyFromFile:(NSString*)derFilePath {
    NSData *derData = [[NSData alloc] initWithContentsOfFile:derFilePath];
    [self loadPublicKeyFromData: derData];
}

- (void)loadPublicKeyFromData:(NSData*)derData {
    publicKey = [self getPublicKeyRefrenceFromeData: derData];
}

- (void)loadPrivateKeyFromFile:(NSString*)p12FilePath password:(NSString*)p12Password {
    NSData *p12Data = [NSData dataWithContentsOfFile:p12FilePath];
    [self loadPrivateKeyFromData: p12Data password:p12Password];
}

- (void)loadPrivateKeyFromData:(NSData*)p12Data password:(NSString*)p12Password {
    privateKey = [self getPrivateKeyRefrenceFromData: p12Data password: p12Password];
}


#pragma mark - Private Methods

- (SecKeyRef)getPublicKeyRefrenceFromeData:(NSData*)derData
{
    SecCertificateRef myCertificate = SecCertificateCreateWithData(kCFAllocatorDefault, (__bridge CFDataRef)derData);
    SecPolicyRef myPolicy = SecPolicyCreateBasicX509();
    SecTrustRef myTrust;
    OSStatus status = SecTrustCreateWithCertificates(myCertificate,myPolicy,&myTrust);
    SecTrustResultType trustResult;
    if (status == noErr) {
        status = SecTrustEvaluate(myTrust, &trustResult);
    }
    SecKeyRef securityKey = SecTrustCopyPublicKey(myTrust);
    CFRelease(myCertificate);
    CFRelease(myPolicy);
    CFRelease(myTrust);
    
    return securityKey;
}

- (SecKeyRef)getPrivateKeyRefrenceFromData:(NSData*)p12Data password:(NSString*)password
{
    SecKeyRef privateKeyRef = NULL;
    NSMutableDictionary * options = [[NSMutableDictionary alloc] init];
    [options setObject: password forKey:(__bridge id)kSecImportExportPassphrase];
    CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
    OSStatus securityError = SecPKCS12Import((__bridge CFDataRef) p12Data, (__bridge CFDictionaryRef)options, &items);
    if (securityError == noErr && CFArrayGetCount(items) > 0) {
        CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
        SecIdentityRef identityApp = (SecIdentityRef)CFDictionaryGetValue(identityDict, kSecImportItemIdentity);
        securityError = SecIdentityCopyPrivateKey(identityApp, &privateKeyRef);
        if (securityError != noErr) {
            privateKeyRef = NULL;
        }
    }
    CFRelease(items);
    
    return privateKeyRef;
}


#pragma mark - Encrypt

- (NSString*)rsaEncryptString:(NSString*)string {
    NSData* data = [string dataUsingEncoding:NSUTF8StringEncoding];
    NSData* encryptedData = [self rsaEncryptData: data];
    NSString* base64EncryptedString = [encryptedData base64EncodedStringWithOptions:0];
    return base64EncryptedString;
}

// 加密的大小受限于SecKeyEncrypt函数，SecKeyEncrypt要求明文和密钥的长度一致，如果要加密更长的内容，需要把内容按密钥长度分成多份，然后多次调用SecKeyEncrypt来实现
- (NSData*)rsaEncryptData:(NSData*)data {
    SecKeyRef key = [self getPublicKey];
    size_t cipherBufferSize = SecKeyGetBlockSize(key);
    uint8_t *cipherBuffer = malloc(cipherBufferSize * sizeof(uint8_t));
    size_t blockSize = cipherBufferSize - 11;       // 分段加密
    size_t blockCount = (size_t)ceil([data length] / (double)blockSize);
    NSMutableData *encryptedData = [[NSMutableData alloc] init] ;
    for (int i=0; i<blockCount; i++) {
        unsigned long bufferSize = MIN(blockSize,[data length] - i * blockSize);
        NSData *buffer = [data subdataWithRange:NSMakeRange(i * blockSize, bufferSize)];
        OSStatus status = SecKeyEncrypt(key, kSecPaddingPKCS1, (const uint8_t *)[buffer bytes], [buffer length], cipherBuffer, &cipherBufferSize);
        if (status == noErr){
            NSData *encryptedBytes = [[NSData alloc] initWithBytes:(const void *)cipherBuffer length:cipherBufferSize];
            [encryptedData appendData:encryptedBytes];
        }else{
            if (cipherBuffer) {
                free(cipherBuffer);
            }
            return nil;
        }
    }
    if (cipherBuffer){
        free(cipherBuffer);
    }
    return encryptedData;
}


#pragma mark - Decrypt

- (NSString*)rsaDecryptString:(NSString*)string {
    NSData* data = [[NSData alloc] initWithBase64EncodedString:string options:NSDataBase64DecodingIgnoreUnknownCharacters];
    NSData* decryptData = [self rsaDecryptData: data];
    NSString* result = [[NSString alloc] initWithData: decryptData encoding:NSUTF8StringEncoding];
    return result;
}

- (NSData*)rsaDecryptData:(NSData*)data {
    SecKeyRef key = [self getPrivateKey];
    size_t cipherLen = [data length];
    void *cipher = malloc(cipherLen);
    [data getBytes:cipher length:cipherLen];
    size_t plainLen = SecKeyGetBlockSize(key) - 12;
    void *plain = malloc(plainLen);
    OSStatus status = SecKeyDecrypt(key, kSecPaddingPKCS1, cipher, cipherLen, plain, &plainLen);
    
    if (status != noErr) {
        return nil;
    }
    
    NSData *decryptedData = [[NSData alloc] initWithBytes:(const void *)plain length:plainLen];
    
    return decryptedData;
}

#pragma marke - verify file SHA1
- (BOOL)rsaSHA1VerifyData:(NSData *)plainData withSignature:(NSData *)signature {
    
    size_t signedHashBytesSize = SecKeyGetBlockSize([self getPublicKey]);
    const void* signedHashBytes = [signature bytes];
    
    size_t hashBytesSize = CC_SHA1_DIGEST_LENGTH;
    uint8_t* hashBytes = malloc(hashBytesSize);
    if (!CC_SHA1([plainData bytes], (CC_LONG)[plainData length], hashBytes)) {
        return NO;
    }
    
    OSStatus status = SecKeyRawVerify(publicKey,
                                      kSecPaddingPKCS1SHA1,
                                      hashBytes,
                                      hashBytesSize,
                                      signedHashBytes,
                                      signedHashBytesSize);
    
    return status == errSecSuccess;
}

@end

#import <Foundation/Foundation.h>
#import "RSACryptographic.h"

/**************** The following methods are decryption/encryption by using a certificate   ****************/
NSString * EncryptoString(NSString *inputStr)
{
    RSACryptographic *rsa = [[RSACryptographic alloc] init];
    
    //Load your public Key file
    [rsa loadPublicKeyFromFile:@"/Users/VictorZhang/Desktop/RSA/public_key.der"];
    
    //encrypt
    return [rsa rsaEncryptString:inputStr];
}

NSString *DecryptoString(NSString *secureText)
{
    RSACryptographic *rsa = [[RSACryptographic alloc] init];
    
    //Load your private key file
    [rsa loadPrivateKeyFromFile:@"/Users/VictorZhang/Desktop/RSA/private_key.p12" password:@"123456"];
    
    //decrypt
    return [rsa rsaDecryptString:secureText];
}


int main(int argc, const char * argv[]) {

      //1.Encrypt String
      NSString *hello = @"Hello world!";
      NSString *secureHello = EncryptoString(hello);
      NSLog(@"Cipher Data : %@", secureHello);
    
      //2.Decrypt String
      NSString *decryptStr = DecryptoString(secureHello);
      NSLog(@"Decrypted Data: %@", decryptStr);

      return 0;
 }