这篇文章主要介绍如下几种加密方式：
- base64
- md5
- AES
- RSA
在示例代码里面，没有专门写工具类，而是直接对NSString 写的分类，所有方法的调用直接采用[NSString xxxMethod]; 的形式。
好了，不废话，直接上代码。
base64加解密
1、加密过程：
NSString+EncryptVerbHandle.h 文件如下：
/**
base64加密
@param str 目标字符串
@return 加密后的字符串
*/
+ (NSString *) base64EncodeFromString:(NSString *) str;
NSString+EncryptVerbHandle.m 文件如下：
+ (NSString *)base64EncodeFromString:(NSString *)str{
//1、先将string转化为data二进制数据
NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
//2、对二进制数据进行base64编码，返回编码后的字符串
return [data base64EncodedStringWithOptions:0];
}
2、解密过程：
NSString+EncryptVerbHandle.h 文件如下：
/**
base64解密
@param str 目标字符串
@return 解密后的字符串
*/
+ (NSString *) base64DecodeFromString:(NSString *) str;
NSString+EncryptVerbHandle.m 文件如下：
+ (NSString *)base64DecodeFromString:(NSString *)str{
//1、先将base64编码后的字符串『解码』为二进制数据
NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:0];
//2、把二进制数据转换为字符串返回
return [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
}
MD5加密
由于md5无法解密（某些网站上的解密方法只是通过大型数据库的匹配比较来实现的），故本文只介绍加密过程。
NSString+EncryptVerbHandle.h 文件如下：
/**
MD5加密算法
MD5加密是单向的，只能加密不能解密.
【MD5加密特点】：
1、压缩性：任意长度的数据，算出的MD5值长度都是固定的。
2、容易计算：从原数据计算出MD5值很容易。
3、抗修改性：对原数据进行任何改动，哪怕只修改1个字节，所得到的MD5值都有很大区别。
4、强抗碰撞：已知原数据和其MD5值，想找到一个具有相同MD5值的数据（即伪造数据）是非常困难的。
@param str 目标字符串
@return md5加密后的字符串
*/
+ (NSString *) md5String:(NSString *) str;
NSString+EncryptVerbHandle.m 文件如下：
+ (NSString *)md5String:(NSString *)str{
const char *cStr = [str UTF8String];
unsigned char digest[CC_MD5_DIGEST_LENGTH];
CC_MD5( cStr, (CC_LONG)strlen(cStr), digest);
NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)
[output appendFormat:@"%02x", digest[i]];
return output;
}
AES加解密
1、加密过程：
NSString+EncryptVerbHandle.h 文件如下：
/**
AES加密算法
@param str 要加密的字符串
@return 加密后的字符串
*/
+ (NSString *) aes256_encrypt:(NSString *) str;
NSString+EncryptVerbHandle.m 文件如下：
+ (NSString *)aes256_encrypt:(NSString *)str{
char keyPtr[kCCKeySizeAES256 + 1];
bzero(keyPtr, sizeof(keyPtr));
/*AES加密与解密的秘钥，需要与后台协商共同定义，保持与后台的秘钥相同*/
[AES_KEY getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
NSData *sourceData = [str dataUsingEncoding:NSUTF8StringEncoding];
NSUInteger dataLength = [sourceData length];
size_t buffersize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(buffersize);
size_t numBytesEncrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode, keyPtr, kCCBlockSizeAES128, NULL, [sourceData bytes], dataLength, buffer, buffersize, &numBytesEncrypted);
if (cryptStatus == kCCSuccess) {
NSData *encryptData = [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
//对加密后的二进制数据进行base64转码
return [encryptData base64EncodedStringWithOptions:NSDataBase64EncodingEndLineWithLineFeed];
}else{
free(buffer);
return nil;
}
}
2、解密过程：
NSString+EncryptVerbHandle.h 文件如下：
/**
AES解密算法
@param str 要解密的字符串
@return 解密后的字符串
*/
+ (NSString *) aes256_decrypt:(NSString *) str;
NSString+EncryptVerbHandle.m 文件如下：
+ (NSString *)aes256_decrypt:(NSString *)str{
//先对加密的字符串进行base64解码
NSData *decodeData = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
char keyPtr[kCCKeySizeAES256 + 1];
bzero(keyPtr, sizeof(keyPtr));
/*AES加密与解密的秘钥，需要与后台协商共同定义，保持与后台的秘钥相同*/
[AES_KEY getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
NSUInteger dataLength = [decodeData length];
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(bufferSize);
size_t numBytesDecrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding | kCCOptionECBMode, keyPtr, kCCBlockSizeAES128, NULL, [decodeData bytes], dataLength, buffer, bufferSize, &numBytesDecrypted);
if (cryptStatus == kCCSuccess) {
NSData *data = [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
return result;
}else{
free(buffer);
return nil;
}
}
RSA加解密
【注意】采用公钥字符串加密和私钥字符串解密需要在工程中做如下设置：
TARGETS->Capabilities->Keychain Sharing-> 打开开关ON
Xcode工程设置
公钥字符串和私钥字符串可以在线生成
1、加密过程：
NSString+EncryptVerbHandle.h 文件如下：
/**
* RSA加密方法
*
* @param str 需要加密的字符串
* @param pubKey 公钥字符串
*/
+ (NSString *)rsaEncryptString:(NSString *)str publicKey:(NSString *)pubKey;
NSString+EncryptVerbHandle.m 文件如下：
static NSString *base64_encode_data(NSData *data){
data = [data base64EncodedDataWithOptions:0];
NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
return ret;
}
#pragma mark - RSA公钥字符串加密，秘钥可以在http://web.chacuo.net/netrsakeypair里生成
+ (NSString *)rsaEncryptString:(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;
}
2、解密过程：
NSString+EncryptVerbHandle.h 文件如下：
/**
* RSA解密方法
*
* @param str 需要解密的字符串
* @param privKey 私钥字符串
*/
+ (NSString *)rsaDecryptString:(NSString *)str privateKey:(NSString *)privKey;
NSString+EncryptVerbHandle.m 文件如下：
static NSData *base64_decode(NSString *str){
NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
return data;
}
#pragma mark - RSA私钥字符串解密
+ (NSString *)rsaDecryptString:(NSString *)str privateKey:(NSString *)privKey{
if (!str) return nil;
NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:0];
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;
}
