RSA der加密 p12解密以及配合AES使用详解

 

在前面的文章中我有说过AES和RSA这两种加密方式，正好在前段时间再项目中有使用到，在这里再把这两种加密方式综合在一起写一下，具体到他们的使用，以及RSA各种加密文件的生成。

 

一： RSA各种加密相关文件生成

---

 

1、首先生成私钥（1024）

$ openssl genrsa -out private_key.pem 1024

    上面是生成了一个名为 private_key 的pem文件，也就是我们的私钥文件，他其实就是一个简单的txt文本文件而已。

 

2、生成证书请求文件

$ openssl req -new -key private_key.pem -out rsacert.csr

     上面命令中的 private_key.pem 就是我们的私钥文件，你会根据它生成一份名为 rsacert 的 csr 文件，当然这个名字是由你定义的。回车之后他会提示你输入国家、省份、mail等信息，当然你也可以什么都不填全部回车。大致是下面图的信息：

 

      通过上面的命令你有了一份 rsacert.csr 文件。

 

3、生成证书并且签名，我们设置有效期为10年，当然这个时间也是你自己定义的

$ openssl x509 -req -days 3650 -in rsacert.csr -signkey private_key.pem -out rsacert.crt

 

4、生成iOS要是用的公钥文件，文件格式为der格式，文件为 public_key.der （名字自己定义）

$ openssl x509 -outform der -in rsacert.crt -out public_key.der

 

5、生成iOS要使用的私钥，为p12格式（名字写了p.p12 这个自己定义）

$ openssl pkcs12 -export -out p.p12 -inkey private_key.pem -in rsacert.crt

       这里我们需要自己注意的点：这一步会提示给私钥文件设置密码，直接输入想要设置密码即可，然后敲回车，然后再验证刚才设置的密码，再次输入密码，然后敲回车，就可以验证了，设置密码是因为在解密时，private_key.p12文件需要和这里设置的密码配合使用，因此需要牢记此密码。具体的使用砸下面的代码中我们会展示出来怎么使用。

 

6、要是单单的iOS加密所需要的文件我们在这里也就已经设置OK了，但安卓一般在使用公钥的使用会用pem格式的公钥，所以这里我们还是需要再处理一下，在前面我们生成的公钥是der格式的，我们在生成一份pem格式的：

$ openssl rsa -in private_key.pem -out rsa_public_key.pem -pubout

 

7、安卓或者Java的同学肯定也需要私钥验证配合我们退耳机数据的，但他们需要的私钥都是PKCS8格式的，  所以我们还需要把我们pem格式的私钥转成PKCS8格式的：

$ openssl pkcs8 -topk8 -in private_key.pem -out pkcs8_private_key.pem -nocrypt

 

      通过上面的这么多步，我们需要的各种格式的文件我们就都创建完成了。大概如下图所示：

 

 

二：准备完成、解释一下为什么要配合使用

---

  

      说说为什么要他们配合使用：

      要是我们单纯的使用AES，AES都知道是对称性加密，对称性的意思就是说加密和解密用的是同一个KEY，当我们移动端把数据加密完的时候我们把数据传给后端，这时候后端要想解开这个加密的数据就需要知道你是用什么KEY加密的，这时候可能有同学会想，那我们和后端定义相同的KEY不就OK了吗，嗯....那后端的KEY就保存在哎服务器，移动端的呢？写在本地还是去服务端请求？都不可以。因为用过这两种方式那安全性就没办法保证了。你写在本地的可以反编译你的代码，要是去服务端请求那就能被人劫持，只要知道了这个KEY那你的加密就变得毫无意义！但至少我们知道了一点，这个KEY很重要！

      很重要那我们该怎么处理呢，这时候就回到我们前面说的正题，AES和RSA配合使用，这个KEY的安全性就通过我们的RSA非对对称性加密保证，对称性就是加密解密要使用同一个KEY，非对称性可肯定就是加密和解密不能使用同一个KEY了，那就是我们的公钥和私钥，公钥加密私钥解密，把我们的KEY通过公钥加密之后上传服务器，服务端拿到之后通过私钥解密就拿到了KEY，再去解密我们的AES数据，有同学会想，前面说我们的AES的KEY可能会被劫持，那加了密被劫持呢，放心被劫持到的也是我们通过公钥加密的，想要得知真正的KEY就得知道我们的私钥，可私钥在我们服务端要想拿到除非有了间谍，不然是没法解开真正的KEY的，还有人可能会想，我们使用公钥加密的KEY我们的公钥就要保存在我们移动端的本地了，那别人拿到公钥之后会不会解开劫持得到的数据呢，不会的，因为公钥加密的只能用私钥解开。

 

三：解释完成，该上代码了

---

 

      我们先看RSA加密的代码，代码具体的都有注释，使用时候需要我们注意的我们在下面说，下面是这个.m文件的代码：

#import "RSAEncryptor.h"
#import 

@implementation RSAEncryptor

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 nil;
    return [self encryptString:str publicKeyRef:[self getPublicKeyRefWithContentsOfFile:path]];
}

//获取公钥
+ (SecKeyRef)getPublicKeyRefWithContentsOfFile:(NSString *)filePath{
    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 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 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 */
@end

 

      注意： 在我们使用RSA的p12文件解密的时候 也就是使用下面这个方法的时候：

   + (NSString *)decryptString:(NSString *)str privateKeyWithContentsOfFile:(NSString *)path password:(NSString *)password

      使用到的 password 的这个参数就是我们给 p12文件设置的密码。这也是为什么前面我们说的你的记住这个密码的原因，不然你只能重新生成了。当然服务端解密的时候是不需要的。

      path 这个参数就是你的p12文件在你本地的路径，这个就自己写了。

 

四：AES呢

---

  

      首先的说说AES我们需要注意的几个点：

      1、加密位数   128还是256的这个得几个端统一不能说你用256的服务端解的时候用128的。

      2、IV 初始向量  这个也得统一，一般128的加密位数使用16位的初始向量

      3、具体的AES加密代码的注释我在前面的博客中有写，它里面参数的含义是什么都有说明，这里就简单的看一下128加密代码，要是想看这个加密方法的具体说明，找一下以前的博客。

     4、string的加密解密还是归结到data的加密解密了，先看data的加密解密：

#import "NSData+AES.h"

static NSString * const AES_IV = @"自己定义";

@implementation NSData (AES)
- (NSData *)aes128_encrypt:(NSString *)key   //加密
{
    // kCCKeySizeAES256是加密位数
    /*
     enum {
     kCCKeySizeAES128          = 16,
     kCCKeySizeAES192          = 24,
     kCCKeySizeAES256          = 32,
     kCCKeySizeDES             = 8,
     kCCKeySize3DES            = 24,
     kCCKeySizeMinCAST         = 5,
     kCCKeySizeMaxCAST         = 16,
     kCCKeySizeMinRC4          = 1,
     kCCKeySizeMaxRC4          = 512,
     kCCKeySizeMinRC2          = 1,
     kCCKeySizeMaxRC2          = 128,
     kCCKeySizeMinBlowfish     = 8,
     kCCKeySizeMaxBlowfish     = 56,
     };
     */
    char keyPtr[kCCKeySizeAES128+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void * buffer = malloc(bufferSize);
    size_t numBytesEncrypted = 0;
    
    //
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding,
                                          keyPtr, kCCBlockSizeAES128,
                                          [AES_IV UTF8String],
                                          [self bytes], dataLength,
                                          buffer, bufferSize,
                                          &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    free(buffer);
    return nil;
}

- (NSData *)aes128_decrypt:(NSString *)key   //解密
{
    char keyPtr[kCCKeySizeAES128+1];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding ,
                                          keyPtr, kCCBlockSizeAES128,
                                          [AES_IV UTF8String],
                                          [self bytes], dataLength,
                                          buffer, bufferSize,
                                          &numBytesDecrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
        
    }
    free(buffer);
    return nil;
}

      5、String的加密解密 128 位的代码如下：

// 利用Key加密字符串
-(NSString *) aes_encrypt:(NSString *)key{
    
    const char *cstr = [self cStringUsingEncoding:NSUTF8StringEncoding];
    NSData *data = [NSData dataWithBytes:cstr length:self.length];
    //对数据进行加密
    NSData *result = [data aes128_encrypt:key];
    
    //转换为2进制字符串
    if (result && result.length > 0) {
        
        Byte *datas = (Byte*)[result bytes];
        NSMutableString *output = [NSMutableString stringWithCapacity:result.length * 2];
        for(int i = 0; i < result.length; i++){
            [output appendFormat:@"%02x", datas[i]];
        }
        return output;
    }
    return nil;
}


//利用Key解密字符串
-(NSString *) aes_decrypt:(NSString *)key{
    
    //转换为2进制Data
    NSMutableData *data = [NSMutableData dataWithCapacity:self.length / 2];
    unsigned char whole_byte;
    char byte_chars[3] = {'\0','\0','\0'};
    int i;
    for (i=0; i < [self length] / 2; i++) {
        byte_chars[0] = [self characterAtIndex:i*2];
        byte_chars[1] = [self characterAtIndex:i*2+1];
        whole_byte = strtol(byte_chars, NULL, 16);
        [data appendBytes:&whole_byte length:1];
    }
    
    //对数据进行解密
    NSData* result = [data aes128_decrypt:key];
    if (result && result.length > 0) {
        return [[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding];
    }
    return nil;
}