iOS中之RSA加密和解密篇

1.RSA算法原理请看：阮一峰老师____RSA算法原理

2.如何通过openssl生成公钥证书和私钥证书

//生成长度为 1024 的私钥：private_key.pem （文件名可自定义）openssl genrsa -out private_key.pem 1024//使用私钥文件创建所需的证书：rsaCertReq.csr（文件名可自定义）openssl req -new -key private_key.pem -out rsaCertReq.csr//使用 x509 创建证书：rsaCert.crt（文件名可自定义）openssl x509 -req -days 3650 -in rsaCertReq.csr -signkey private_key.pem -out rsaCert.crt//生成 .der 格式的公钥：public_key.der（文件名可自定义）openssl x509 -outform der -in rsaCert.crt -out public_key.der//生成解密所需 .p12文件：private_key.p12（文件名可自定义）openssl pkcs12 -export -out private_key.p12 -inkey private_key.pem -in rsaCert.crt在命令行种可能需要你的一些信息去生成公钥和私钥Country Name (2 letter code) [AU]:CN     //国家码State or Province Name (full name) [Some-State]:china    //地区码Locality Name (eg, city) []:shenzhen　　　//本地码Organization Name (eg, company) [Internet Widgits Pty Ltd]:wenSir   //公司名称Organizational Unit Name (eg, section) []:wenSir    //部门Common Name (eg, YOUR name) []:wenSir    //名字Email Address []:　　　　//邮箱

注意：在生成密钥对的时候需要填入私钥的提取密码，用于解密；

3.生成的公钥和私钥证书如下，并导入工程文件中

4.自定义RSA类 RSAEncryptor.h，添加加密解密方法

/** *  加密方法 * *  @param str   需要加密的字符串 *  @param path  '.der'格式的公钥证书文件路径 */+ (NSString *)encryptString:(NSString *)str publicKeyWithContentsOfFile:(NSString *)path;/** *  解密方法 * *  @param str       需要解密的字符串 *  @param path      '.p12'格式的私钥证书文件路径 *  @param password  私钥文件密码 */+ (NSString *)decryptString:(NSString *)str privateKeyWithContentsOfFile:(NSString *)path password:(NSString *)password;/** *  加密方法 * *  @param str    需要加密的字符串 *  @param pubKey 公钥字符串 */+ (NSString *)encryptString:(NSString *)str publicKey:(NSString *)pubKey;/** *  解密方法 * *  @param str     需要解密的字符串 *  @param privKey 私钥字符串 */+ (NSString *)decryptString:(NSString *)str privateKey:(NSString *)privKey;

RSAEncryptor.m中的方法实现

//转译编码static NSString *base64_encode_data(NSData *data){    data = [data base64EncodedDataWithOptions:0];    NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];    return ret;}static NSData *base64_decode(NSString *str){    NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];    return data;}#pragma mark - 使用'.der'公钥文件加密//加密+ (NSString *)encryptString:(NSString *)str publicKeyWithContentsOfFile:(NSString *)path{    if (!str || !path)  return @"encrypt error";    return [self encryptString:str publicKeyRef:[self getPublicKeyRefWithContentsOfFile:path]];}//获取公钥+ (SecKeyRef)getPublicKeyRefWithContentsOfFile:(NSString *)filePath{    //获取data    NSData *certData = [NSData dataWithContentsOfFile:filePath];    if (!certData) {        return nil;    }    SecCertificateRef cert = SecCertificateCreateWithData(NULL, (CFDataRef)certData);    SecKeyRef key = NULL;    SecTrustRef trust = NULL;    SecPolicyRef policy = NULL;    if (cert != NULL) {        policy = SecPolicyCreateBasicX509();        if (policy) {            if (SecTrustCreateWithCertificates((CFTypeRef)cert, policy, &trust) == noErr) {                SecTrustResultType result;                if (SecTrustEvaluate(trust, &result) == noErr) {                    key = SecTrustCopyPublicKey(trust);                }            }        }    }    if (policy) CFRelease(policy);    if (trust) CFRelease(trust);    if (cert) CFRelease(cert);    return key;}+ (NSString *)encryptString:(NSString *)str publicKeyRef:(SecKeyRef)publicKeyRef{    if(![str dataUsingEncoding:NSUTF8StringEncoding]){        return nil;    }    if(!publicKeyRef){        return nil;    }    NSData *data = [self encryptData:[str dataUsingEncoding:NSUTF8StringEncoding] withKeyRef:publicKeyRef];    NSString *ret = base64_encode_data(data);    return ret;}#pragma mark - 使用'.12'私钥文件解密//解密+ (NSString *)decryptString:(NSString *)str privateKeyWithContentsOfFile:(NSString *)path password:(NSString *)password{    if (!str || !path) return nil;    if (!password) password = @"";    return [self decryptString:str privateKeyRef:[self getPrivateKeyRefWithContentsOfFile:path password:password]];}//获取私钥+ (SecKeyRef)getPrivateKeyRefWithContentsOfFile:(NSString *)filePath password:(NSString*)password{    NSData *p12Data = [NSData dataWithContentsOfFile:filePath];    if (!p12Data) {        return nil;    }    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;}+ (NSString *)decryptString:(NSString *)str privateKeyRef:(SecKeyRef)privKeyRef{    NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];    if (!privKeyRef) {        return nil;    }    data = [self decryptData:data withKeyRef:privKeyRef];    NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];    return ret;}#pragma mark - 使用公钥字符串加密/* START: Encryption with RSA public key *///使用公钥字符串加密+ (NSString *)encryptString:(NSString *)str publicKey:(NSString *)pubKey{    NSData *data = [self encryptData:[str dataUsingEncoding:NSUTF8StringEncoding] publicKey:pubKey];    NSString *ret = base64_encode_data(data);    return ret;}+ (NSData *)encryptData:(NSData *)data publicKey:(NSString *)pubKey{    if(!data || !pubKey){        return nil;    }    SecKeyRef keyRef = [self addPublicKey:pubKey];    if(!keyRef){        return nil;    }    return [self encryptData:data withKeyRef:keyRef];}+ (SecKeyRef)addPublicKey:(NSString *)key{    NSRange spos = [key rangeOfString:@"-----BEGIN PUBLIC KEY-----"];    NSRange epos = [key rangeOfString:@"-----END PUBLIC KEY-----"];    if(spos.location != NSNotFound && epos.location != NSNotFound){        NSUInteger s = spos.location + spos.length;        NSUInteger e = epos.location;        NSRange range = NSMakeRange(s, e-s);        key = [key substringWithRange:range];    }    key = [key stringByReplacingOccurrencesOfString:@"\r" withString:@""];    key = [key stringByReplacingOccurrencesOfString:@"\n" withString:@""];    key = [key stringByReplacingOccurrencesOfString:@"\t" withString:@""];    key = [key stringByReplacingOccurrencesOfString:@" "  withString:@""];    // This will be base64 encoded, decode it.    NSData *data = base64_decode(key);    data = [self stripPublicKeyHeader:data];    if(!data){        return nil;    }    //a tag to read/write keychain storage    NSString *tag = @"RSAUtil_PubKey";    NSData *d_tag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];    // Delete any old lingering key with the same tag    NSMutableDictionary *publicKey = [[NSMutableDictionary alloc] init];    [publicKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];    [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];    [publicKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];    SecItemDelete((__bridge CFDictionaryRef)publicKey);    // Add persistent version of the key to system keychain    [publicKey setObject:data forKey:(__bridge id)kSecValueData];    [publicKey setObject:(__bridge id) kSecAttrKeyClassPublic forKey:(__bridge id)     kSecAttrKeyClass];    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)     kSecReturnPersistentRef];    CFTypeRef persistKey = nil;    OSStatus status = SecItemAdd((__bridge CFDictionaryRef)publicKey, &persistKey);    if (persistKey != nil){        CFRelease(persistKey);    }    if ((status != noErr) && (status != errSecDuplicateItem)) {        return nil;    }    [publicKey removeObjectForKey:(__bridge id)kSecValueData];    [publicKey removeObjectForKey:(__bridge id)kSecReturnPersistentRef];    [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];    [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];    // Now fetch the SecKeyRef version of the key    SecKeyRef keyRef = nil;    status = SecItemCopyMatching((__bridge CFDictionaryRef)publicKey, (CFTypeRef *)&keyRef);    if(status != noErr){        return nil;    }    return keyRef;}+ (NSData *)stripPublicKeyHeader:(NSData *)d_key{    // Skip ASN.1 public key header    if (d_key == nil) return(nil);    unsigned long len = [d_key length];    if (!len) return(nil);    unsigned char *c_key = (unsigned char *)[d_key bytes];    unsigned int  idx     = 0;    if (c_key[idx++] != 0x30) return(nil);    if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;    else idx++;    // PKCS #1 rsaEncryption szOID_RSA_RSA    static unsigned char seqiod[] =    { 0x30,   0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01,        0x01, 0x05, 0x00 };    if (memcmp(&c_key[idx], seqiod, 15)) return(nil);    idx += 15;    if (c_key[idx++] != 0x03) return(nil);    if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;    else idx++;    if (c_key[idx++] != '\0') return(nil);    // Now make a new NSData from this buffer    return ([NSData dataWithBytes:&c_key[idx] length:len - idx]);}+ (NSData *)encryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef{    const uint8_t *srcbuf = (const uint8_t *)[data bytes];    size_t srclen = (size_t)data.length;    size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);    void *outbuf = malloc(block_size);    size_t src_block_size = block_size - 11;    NSMutableData *ret = [[NSMutableData alloc] init];    for(int idx=0; idx<srclen; idx+=src_block_size){        //NSLog(@"%d/%d block_size: %d", idx, (int)srclen, (int)block_size);        size_t data_len = srclen - idx;        if(data_len > src_block_size){            data_len = src_block_size;        }        size_t outlen = block_size;        OSStatus status = noErr;        status = SecKeyEncrypt(keyRef,                               kSecPaddingPKCS1,                               srcbuf + idx,                               data_len,                               outbuf,                               &outlen                               );        if (status != 0) {            NSLog(@"SecKeyEncrypt fail. Error Code: %d", status);            ret = nil;            break;        }else{            [ret appendBytes:outbuf length:outlen];        }    }    free(outbuf);    CFRelease(keyRef);    return ret;}/* END: Encryption with RSA public key */#pragma mark - 使用私钥字符串解密/* START: Decryption with RSA private key *///使用私钥字符串解密+ (NSString *)decryptString:(NSString *)str privateKey:(NSString *)privKey{    if (!str) return nil;    NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];    data = [self decryptData:data privateKey:privKey];    NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];    return ret;}+ (NSData *)decryptData:(NSData *)data privateKey:(NSString *)privKey{    if(!data || !privKey){        return nil;    }    SecKeyRef keyRef = [self addPrivateKey:privKey];    if(!keyRef){        return nil;    }    return [self decryptData:data withKeyRef:keyRef];}+ (SecKeyRef)addPrivateKey:(NSString *)key{    NSRange spos = [key rangeOfString:@"-----BEGIN RSA PRIVATE KEY-----"];    NSRange epos = [key rangeOfString:@"-----END RSA PRIVATE KEY-----"];    if(spos.location != NSNotFound && epos.location != NSNotFound){        NSUInteger s = spos.location + spos.length;        NSUInteger e = epos.location;        NSRange range = NSMakeRange(s, e-s);        key = [key substringWithRange:range];    }    key = [key stringByReplacingOccurrencesOfString:@"\r" withString:@""];    key = [key stringByReplacingOccurrencesOfString:@"\n" withString:@""];    key = [key stringByReplacingOccurrencesOfString:@"\t" withString:@""];    key = [key stringByReplacingOccurrencesOfString:@" "  withString:@""];    // This will be base64 encoded, decode it.    NSData *data = base64_decode(key);    data = [self stripPrivateKeyHeader:data];    if(!data){        return nil;    }    //a tag to read/write keychain storage    NSString *tag = @"RSAUtil_PrivKey";    NSData *d_tag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];    // Delete any old lingering key with the same tag    NSMutableDictionary *privateKey = [[NSMutableDictionary alloc] init];    [privateKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];    [privateKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];    [privateKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];    SecItemDelete((__bridge CFDictionaryRef)privateKey);    // Add persistent version of the key to system keychain    [privateKey setObject:data forKey:(__bridge id)kSecValueData];    [privateKey setObject:(__bridge id) kSecAttrKeyClassPrivate forKey:(__bridge id)     kSecAttrKeyClass];    [privateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)     kSecReturnPersistentRef];    CFTypeRef persistKey = nil;    OSStatus status = SecItemAdd((__bridge CFDictionaryRef)privateKey, &persistKey);    if (persistKey != nil){        CFRelease(persistKey);    }    if ((status != noErr) && (status != errSecDuplicateItem)) {        return nil;    }    [privateKey removeObjectForKey:(__bridge id)kSecValueData];    [privateKey removeObjectForKey:(__bridge id)kSecReturnPersistentRef];    [privateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];    [privateKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];    // Now fetch the SecKeyRef version of the key    SecKeyRef keyRef = nil;    status = SecItemCopyMatching((__bridge CFDictionaryRef)privateKey, (CFTypeRef *)&keyRef);    if(status != noErr){        return nil;    }    return keyRef;}+ (NSData *)stripPrivateKeyHeader:(NSData *)d_key{    // Skip ASN.1 private key header    if (d_key == nil) return(nil);    unsigned long len = [d_key length];    if (!len) return(nil);    unsigned char *c_key = (unsigned char *)[d_key bytes];    unsigned int  idx     = 22; //magic byte at offset 22    if (0x04 != c_key[idx++]) return nil;    //calculate length of the key    unsigned int c_len = c_key[idx++];    int det = c_len & 0x80;    if (!det) {        c_len = c_len & 0x7f;    } else {        int byteCount = c_len & 0x7f;        if (byteCount + idx > len) {            //rsa length field longer than buffer            return nil;        }        unsigned int accum = 0;        unsigned char *ptr = &c_key[idx];        idx += byteCount;        while (byteCount) {            accum = (accum << 8) + *ptr;            ptr++;            byteCount--;        }        c_len = accum;    }    // Now make a new NSData from this buffer    return [d_key subdataWithRange:NSMakeRange(idx, c_len)];}+ (NSData *)decryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef{    const uint8_t *srcbuf = (const uint8_t *)[data bytes];    size_t srclen = (size_t)data.length;    size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);    UInt8 *outbuf = malloc(block_size);    size_t src_block_size = block_size;    NSMutableData *ret = [[NSMutableData alloc] init];    for(int idx=0; idx<srclen; idx+=src_block_size){        //NSLog(@"%d/%d block_size: %d", idx, (int)srclen, (int)block_size);        size_t data_len = srclen - idx;        if(data_len > src_block_size){            data_len = src_block_size;        }        size_t outlen = block_size;        OSStatus status = noErr;        status = SecKeyDecrypt(keyRef,                               kSecPaddingNone,                               srcbuf + idx,                               data_len,                               outbuf,                               &outlen                               );        if (status != 0) {            NSLog(@"SecKeyEncrypt fail. Error Code: %d", status);            ret = nil;            break;        }else{            //the actual decrypted data is in the middle, locate it!            int idxFirstZero = -1;            int idxNextZero = (int)outlen;            for ( int i = 0; i < outlen; i++ ) {                if ( outbuf[i] == 0 ) {                    if ( idxFirstZero < 0 ) {                        idxFirstZero = i;                    } else {                        idxNextZero = i;                        break;                    }                }            }            [ret appendBytes:&outbuf[idxFirstZero+1] length:idxNextZero-idxFirstZero-1];        }    }    free(outbuf);    CFRelease(keyRef);    return ret;}/* END: Decryption with RSA private key */

5.RSAEncryptor类中方法的调用和实现加密解密

//加密响应事件- (IBAction)encryptionAction:(UIButton *)sender {    //显示加密之后的字符串    self.encryShowLabel.text = [RSAEncryptor encryptString:self.textField.text publicKeyWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"public_key" ofType:@"der"]];}//解密响应事件- (IBAction)decryptAction:(UIButton *)sender {    //显示还原的字符串    self.decryptShowLabel.text = [RSAEncryptor decryptString:self.encryShowLabel.text privateKeyWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"private_key" ofType:@"p12"] password:@"wensir2513"];}

6.效果图，Demo链接RSADemo文件