之前的项目中接触过一些加密的方法，也没有太仔细的进行记录和研究。最近在写SDK时，加密模块的占比相当之大；借此时机，对我们常用的加密方式做一个笔记。
为什么要做加密操作？
加密就是为了保证我们的数据安全，即不被他人篡改或截取到有用的信息的操作。iOS一直以安全著称，但是从Xcode的Ghost事件之后，iOS安全不可摧的神话似乎已经被打破。事实证明，无论是Android还是iOS，该加密处理的还是需要加密处理，谁也不能保证自己一定是安全的。下面我们来介绍iOS常用到的加密方式。
iOS常用加密方式
常见的iOS代码加密常用加密方式包括Base64加密、MD5加密、AES加密、RSA加密等。无论选择哪种加密算法，最终都是为了保证代码安全，捍卫自己的产品原创性。
Base64加密
Base64编码的思想是：采用64个基本的ASCII码字符对数据进行重新编码。它将需要编码的数据拆分成字节数组，以3个字节为一组，按顺序排列24位数据，再把这24位数据分成4组，即每组6位；再在每组的的最高位前补两个0凑足一个字节，这样就把一个3字节为一组的数据重新编码成了4个字节；当所要编码的数据的字节数不是3的整倍数，也就是说在分组时最后一组不够3个字节，这时在最后一组填充1到2个0字节，并在最后编码完成后在结尾添加1到2个=号。例如：将对ABC进行Base64编码首先取ABC对应的ASCII码值，A : 65、B : 66、C : 67，再取二进制值A : 01000001、B : 01000010、C : 01000011，然后把这三个字节的二进制码接起来010000010100001001000011，再以6位为单位分成4个数据块并在最高位填充两个0后形成4个字节的编码后的值00010000、00010100、00001001、00000011；再把这4个字节数据转化成10进制数得16、20、19、3；最后根据Base64给出的64个基本字符表，查出对应的ASCII码字符Q、U、J、D，这里的值实际就是数据在字符表中的索引。解码过程就是把4个字节再还原成3个字节再根据不同的数据形式把字节数组重新整理成数据。注：Base64字符表，包括大写A-Z小写a-z数字0-9和+以及/。
Base64加密原则：6bit（原8bit）一个字节，不足的位数用0补齐，两个0用一个=表示。
Base64加密特点：
1. `- 数据加密之后，数据量会变大，变大1/3左右。`
2. `- 可进行反向解密。`
3. `- 编码后有个非常显著的特点，末尾有个=号。`
在iOS中Base64加解密使用方法介绍（本例使用系统API，仅支持iOS7及以后的系统版本）
1. `/****************************Base64.m类实现文件内容****************************/`
2. `+ (NSString *)base64EncodedStringWithData:(NSData *)data`
3. `{`
4. `//判断是否传入需要加密数据参数`
5. `if ((data == nil) || (data == NULL)) {`
6. `return nil;`
7. `} else if (![data isKindOfClass:[NSData class]]) {`
8. `return nil;`
9. `}`
10. `//判断设备系统是否满足条件`
11. `if ([[[UIDevice currentDevice] systemVersion] doubleValue] <= 6.9) {`
12. `return nil;`
13. `}`
14. `//使用系统的API进行Base64加密操作`
15. `NSDataBase64EncodingOptions options;`
16. `options = NSDataBase64EncodingEndLineWithLineFeed;`
17. `return [data base64EncodedStringWithOptions:options];`
18. `}`
19. `+ (NSData *)base64DecodeDataWithString:(NSString *)string`
20. `{`
21. `//判断是否传入需要加密数据参数`
22. `if ((string == nil) || (string == NULL)) {`
23. `return nil;`
24. `} else if (![string isKindOfClass:[NSString class]]) {`
25. `return nil;`
26. `}`
27. `//判断设备系统是否满足条件`
28. `if ([[[UIDevice currentDevice] systemVersion] doubleValue] <= 6.9) {`
29. `return nil;`
30. `}`
31. `//使用系统的API进行Base64解密操作`
32. `NSDataBase64DecodingOptions options;`
33. `options = NSDataBase64DecodingIgnoreUnknownCharacters;`
34. `return [[NSData alloc] initWithBase64EncodedString:string options:options];`
35. `}`
36. `/*****************************************************************************/`
37. `//使用Base64文件进行Base64加密和解密`
38. `/*********************************使用Base64类*********************************/`
39. `//使用Base64执行加密操作`
40. `NSString *string = @"abcdefghijklmnopqrstuvwxyz";`
41. `NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];`
42. `NSString *encodeString = [Base64 base64EncodedStringWithData:data];`
43. `NSLog(@"encodeString : %@", encodeString);`
44. `//使用Base64执行解密操作`
45. `NSString *decodeString = nil;`
46. `NSData *decodeData = [Base64 base64DecodeDataWithString:encodeString];`
47. `decodeString = [[NSString alloc] initWithData:decodeData`
48. `encoding:NSUTF8StringEncoding];`
49. `NSLog(@"decodeString : %@", decodeString);`
50. `/******************************************************************************/`
MD5加密（MD5是一种摘要，而非加密，只是经常与加密配合使用）
MD5的全称是Message-DigestAlgorithm 5，Message-Digest泛指字节串(Message)的Hash变换，就是把一个任意长度的字节串变换成一定长的大整数。请注意我使用了字节串而不是字符串这个词，是因为这种变换只与字节的值有关，与字符集或编码方式无关。MD5将任意长度的字节串变换成一个128bit的大整数，并且它是一个不可逆的字符串变换算法，换句话说就是，即使你看到源程序和算法描述，也无法将一个MD5的值变换回原始的字符串，从数学原理上说，是因为原始的字符串有无穷多个，这有点象不存在反函数的数学函数。MD5的典型应用是对一段Message(字节串)产生fingerprint(指纹)，以防止被”篡改”。举个例子，你将一段话写在一个叫readme.txt文件中，并对这个readme.txt产生一个MD5的值并记录在案，然后你可以传播这个文件给别人，别人如果修改了文件中的任何内容，你对这个文件重新计算MD5时就会发现。如果再有一个第三方的认证机构，用MD5还可以防止文件作者的”抵赖”，这就是所谓的数字签名应用。MD5还广泛用于加密和解密技术上，在很多操作系统中，用户的密码是以MD5值（或类似的其它算法）的方式保存的，用户Login的时候，系统是把用户输入的密码计算成MD5值，然后再去和系统中保存的MD5值进行比较，而系统并”不知道”用户的密码是什么。MD5加密大体都应用在：验证数据或文件一致性、数字签名、安全访问认证等等。大概可比喻为：人的指纹来理解。
注：MD5加密是不可逆的，也就是说，MD5加密后是不能解密的，所谓的解密只是用大数据的”试用”，来测出结果的。
MD5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，哪怕只修改一个字节，所得到的MD5值都有很大区别。`
4. `- 弱抗碰撞 : 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。`
5. `- 强抗碰撞 : 想找到两个不同数据，使他们具有相同的MD5值，是非常困难的。`
在iOS中MD5加密和验签使用方法介绍
1. `/****************************MD5.m类实现文件内容****************************/`
2. `//对字符串数据进行MD5的签名`
3. `+ (NSString *)md5SignWithString:(NSString *)string`
4. `{`
5. `const char *object = [string UTF8String];`
6. `unsigned char result[CC_MD5_DIGEST_LENGTH];`
7. `CC_MD5(object,(CC_LONG)strlen(object),result);`
8. `NSMutableString *hash = [NSMutableString string];`
9. `for (int i = 0; i < 16; i ++) {`
10. `[hash appendFormat:@"%02X", result[i]];`
11. `}`
12. `return [hash lowercaseString];`
13. `}`
14. `//对二进制数据进行MD5的签名`
15. `+ (NSData *)md5SignWithData:(NSData *)data`
16. `{`
17. `Byte byte[CC_MD5_DIGEST_LENGTH]; //定义一个字节数组来接收结果`
18. `CC_MD5((const void*)([data bytes]), (CC_LONG)[data length], byte);`
19. `return [NSData dataWithBytes:byte length:CC_MD5_DIGEST_LENGTH];`
20. `}`
21. `/******************************************************************************/`
22. `//使用MD5文件进行MD5加密和验签`
23. `/*********************************使用MD5类*********************************/`
24. `//使用MD5执行加密操作`
25. `NSString *string2 = @"abcdefghijklmnopqrstuvwxyz";`
26. `NSString *encodeString2 = [MD5 md5SignWithString:string2];`
27. `NSLog(@"encodeString2 : %@", encodeString2);`
28. `//MD5为不可逆的操作，使用MD5执行验签操作`
29. `NSString *verifyString2 = [MD5 md5SignWithString:string2];`
30. `NSLog(@"verifyString2 : %@", verifyString2);`
31. `if ([verifyString2 isEqualToString:encodeString2]) {`
32. `NSLog(@"md5 verify sign success");`
33. `} else {`
34. `NSLog(@"md5 verify sign failed");`
35. `}`
36. `/******************************************************************************/`
AES加密
高级加密标准Advanced Encryption Standard简称：AES，在密码学中又称Rijndael加密法，是美国联邦政府采用的一种区块加密标准。它是一种对称加密算法，这个标准也替代原先的DES标准，已经被多方分析且广为全世界所使用。AES设计有三个密钥长度:128、192、256位，相对而言，AES的128密钥比DES的56密钥强1021倍。AES算法主要包括三个方面：轮变化、圈数和密钥扩展。总体来说，AES作为新一代的数据加密标准汇聚了强安全性、高性能、高效率、易用和灵活，在软件及硬件上都能快速地加解密且只需要很少的存储资源等优点。
AES加密流程介绍无从下笔，直接上图了。
image
AES加解密特点：
1. `- AES强安全性、高性能、高效率、易用和灵活。`
2. `- 在软件及硬件上都能快速地加解密且只需要很少的存储资源。`
在iOS中AES加解密的实现介绍
1. `//需要导入：#import <CommonCrypto/CommonCrypto.h>库才能使用`
2. `/**`
3. `* AES128 + ECB + PKCS7`
4. `* @param data 要加密的原始数据`
5. `* @param key 加密 key`
6. `* @return 加密后数据`
7. `*/`
8. `+ (NSData *)encryptData:(NSData *)data key:(NSData *)key`
9. `{`
10. `//判断解密的流数据是否存在`
11. `if ((data == nil) || (data == NULL)) {`
12. `return nil;`
13. `} else if (![data isKindOfClass:[NSData class]]) {`
14. `return nil;`
15. `} else if ([data length] <= 0) {`
16. `return nil;`
17. `}`
18. `//判断解密的Key是否存在`
19. `if ((key == nil) || (key == NULL)) {`
20. `return nil;`
21. `} else if (![key isKindOfClass:[NSData class]]) {`
22. `return nil;`
23. `} else if ([key length] <= 0) {`
24. `return nil;`
25. `}`
26. `//setup key`
27. `NSData *result = nil;`
28. `unsigned char cKey[kCCKeySizeAES128];`
29. `bzero(cKey, sizeof(cKey));`
30. `[key getBytes:cKey length:kCCKeySizeAES128];`
31. `//setup output buffer`
32. `size_t bufferSize = [data length] + kCCBlockSizeAES128;`
33. `void *buffer = malloc(bufferSize);`
34. `//do encrypt`
35. `size_t encryptedSize = 0;`
36. `CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,`
37. `kCCAlgorithmAES128,`
38. `kCCOptionECBMode|kCCOptionPKCS7Padding,`
39. `cKey,`
40. `kCCKeySizeAES128,`
41. `nil,`
42. `[data bytes],`
43. `[data length],`
44. `buffer,`
45. `bufferSize,`
46. `&encryptedSize);`
47. `if (cryptStatus == kCCSuccess) {`
48. `result = [NSData dataWithBytesNoCopy:buffer length:encryptedSize];`
49. `} else {`
50. `free(buffer);`
51. `}`
52. `return result;`
53. `}`
54. `/**`
55. `* AES128 + ECB + PKCS7`
56. `* @param data 要解密的原始数据`
57. `* @param key 解密 key`
58. `* @return 解密后数据`
59. `*/`
60. `+ (NSData *)decryptData:(NSData *)data key:(NSData *)key`
61. `{`
62. `//判断解密的流数据是否存在`
63. `if ((data == nil) || (data == NULL)) {`
64. `return nil;`
65. `} else if (![data isKindOfClass:[NSData class]]) {`
66. `return nil;`
67. `} else if ([data length] <= 0) {`
68. `return nil;`
69. `}`
70. `//判断解密的Key是否存在`
71. `if ((key == nil) || (key == NULL)) {`
72. `return nil;`
73. `} else if (![key isKindOfClass:[NSData class]]) {`
74. `return nil;`
75. `} else if ([key length] <= 0) {`
76. `return nil;`
77. `}`
78. `//setup key`
79. `NSData *result = nil;`
80. `unsigned char cKey[kCCKeySizeAES128];`
81. `bzero(cKey, sizeof(cKey));`
82. `[key getBytes:cKey length:kCCKeySizeAES128];`
83. `//setup output buffer`
84. `size_t bufferSize = [data length] + kCCBlockSizeAES128;`
85. `void *buffer = malloc(bufferSize);`
86. `//do decrypt`
87. `size_t decryptedSize = 0;`
88. `CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,`
89. `kCCAlgorithmAES128,`
90. `kCCOptionECBMode|kCCOptionPKCS7Padding,`
91. `cKey,`
92. `kCCKeySizeAES128,`
93. `nil,`
94. `[data bytes],`
95. `[data length],`
96. `buffer,`
97. `bufferSize,`
98. `&decryptedSize);`
99. `if (cryptStatus == kCCSuccess) {`
100. `result = [NSData dataWithBytesNoCopy:buffer length:decryptedSize];`
101. `} else {`
102. `free(buffer);`
103. `}`
104. `return result;`
105. `}`
在iOS中AES加解密使用方法介绍
1. `//使用AES执行加密操作`
2. `NSString *aesKey = @"a1b2c3d4e5f6g7h8";`
3. `NSString *string3 = @"abcdefghijklmnopqrstuvwxyz";`
4. `NSData *keyData3 = [aesKey dataUsingEncoding:NSUTF8StringEncoding];`
5. `NSData *sourceData3 = [string3 dataUsingEncoding:NSUTF8StringEncoding];`
6. `NSData *encodeData3 = [AESEncrypt encryptData:sourceData3 key:keyData3];`
7. `NSLog(@"encodeData3 : %@", encodeData3);`
8. `//使用AES执行解密操作`
9. `NSString *decodeString3 = nil;`
10. `NSData *decodeData3 = [AESEncrypt decryptData:encodeData3`
11. `key:keyData3];`
12. `decodeString3 = [[NSString alloc] initWithData:decodeData3`
13. `encoding:NSUTF8StringEncoding];`
14. `NSLog(@"decodeString3 : %@", decodeString3);`
RSA加密
RSA是目前最有影响力的公钥加密算法，它能够抵抗到目前为止已知的绝大多数密码攻击，已被ISO推荐为公钥数据加密标准。RSA的公开密钥密码体制就是使用不同的加密密钥与解密密钥，是一种“由已知加密密钥推导出解密密钥在计算上是不可行的”密码体制。通常是先生成一对RSA密钥，其中之一是保密密钥，由用户保存；另一个为公开密钥，可对外公开，甚至可在网络服务器中注册。为提高保密强度，RSA密钥至少为500位长，一般推荐使用1024位，这就使加密的计算量很大。为减少计算量，在传送信息时，常采用传统加密方法与公开密钥加密方法相结合的方式，即信息采用改进的DES或IDEA对话密钥加密，然后使用RSA密钥加密对话密钥和信息摘要，对方收到信息后，用不同的密钥解密并可核对信息摘要。RSA算法是第一个能同时用于加密和数字签名的算法，也易于理解和操作，RSA是被研究得最广泛的公钥算法。RSA算法是一种非对称密码算法，所谓非对称，就是指该算法需要一对密钥，使用其中一个加密，则需要用另一个才能解密。RSA加密大体都应用在：本地数据加密、网络传输数据加密、方法体和方法名高级混淆以及程序结构混排加密。例如：对客户端传输数据提供加密方案，有效防止通过网络接口的拦截获取。
RSA的算法涉及三个参数，n、e1、e2。其中，n是两个大质数p、q的积，n的二进制表示时所占用的位数，就是所谓的密钥长度。e1和e2是一对相关的值，e1可以任意取，但要求e1与(p-1)(q-1)互质；再选择e2，要求(e2e1)mod((p-1)*(q-1))=1。(n，e1)，(n，e2)就是密钥对。其中(n，e1)为公钥，(n，e2)为私钥；RSA加解密的算法完全相同，公钥加密体制中，一般用公钥加密，私钥解密。假设A为明文，B为密文，则：A=B^e2 mod n；B=A^e1 mod n；e1和e2可以互换使用，即私钥加密，公钥解密，公式：A=B^e1 mod n；B=A^e2 mod n;
RSA加解密特点：
1. `- RSA密钥管理的方便，计算量很大速度相对比较慢。`
2. `- RSA安全性很高，能够抵抗到目前为止已知的绝大多数密码攻击。`
在线生成RSA密钥对的网址：在线生成非对称加密公钥私钥对等，RSA密钥格式请使用PKCS#8格式。PKCS#1与PKCS#8的区别还待后续查阅资料，再进行补充记录。
在iOS中RSA加解密的实现介绍（支持密钥文件<.pem>和字符串密钥）
1. `/****************************RSAEncrypt.m类实现文件内容****************************/`
2. `pragma mark - Class Utils Method`
3. `+ (BOOL)isEmptyKeyRef:(id)object`
4. `{`
5. `if (object == nil) {`
6. `return YES;`
7. `} else if (object == NULL) {`
8. `return YES;`
9. `} else if (object == [NSNull null]) {`
10. `return YES;`
11. `}`
12. `return NO;`
13. `}`
14. `pragma mark - Private Method`
15. `+ (SecKeyRef)getPrivateKeyRefWithFilePath:(NSString *)filePath keyPassword:(NSString *)keyPassword`
16. `{`
17. `//读取私钥证书文件的内容`
18. `NSData *certificateData = [NSData dataWithContentsOfFile:filePath];`
19. `if ((certificateData == nil) || (certificateData == NULL)) {`
20. `return nil;`
21. `} else if (![certificateData isKindOfClass:[NSData class]]) {`
22. `return nil;`
23. `} else if ([certificateData length] <= 0) {`
24. `return nil;`
25. `}`
26. `//拼接密码参数到字典中`
27. `NSString *passwordKey = (__bridge id)kSecImportExportPassphrase;`
28. `NSString *passwordValue = [NSString stringWithFormat:@"%@",keyPassword];`
29. `if ((keyPassword == nil) || (keyPassword == NULL)) {`
30. `passwordValue = @"";`
31. `} else if (![keyPassword isKindOfClass:[NSString class]]) {`
32. `passwordValue = @"";`
33. `} else if ([keyPassword length] <= 0) {`
34. `passwordValue = @"";`
35. `}`
36. `NSMutableDictionary *optionInfo = [[NSMutableDictionary alloc] init];`
37. `[optionInfo setObject:passwordValue forKey:passwordKey];`
38. `//获取私钥对象`
39. `SecKeyRef privateKeyRef = NULL;`
40. `CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);`
41. `CFDataRef pkcs12Data = (__bridge CFDataRef)certificateData;`
42. `CFDictionaryRef options = (__bridge CFDictionaryRef)optionInfo;`
43. `OSStatus securityStatus = SecPKCS12Import(pkcs12Data, options, &items);`
44. `if (securityStatus == noErr && CFArrayGetCount(items) > 0)`
45. `{`
46. `SecIdentityRef identity;`
47. `const void *secpkey = kSecImportItemIdentity;`
48. `CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);`
49. `identity = (SecIdentityRef)CFDictionaryGetValue(identityDict,secpkey);`
50. `securityStatus = SecIdentityCopyPrivateKey(identity, &privateKeyRef);`
51. `if (securityStatus != noErr)`
52. `{`
53. `privateKeyRef = NULL;`
54. `}`
55. `}`
56. `CFRelease(items);`
57. `return privateKeyRef;`
58. `}`
59. `+ (SecKeyRef)privateKeyRefWithPrivateKey:(NSString *)privateKey`
60. `{`
61. `//判断参数是否正确`
62. `if ((privateKey == nil) || (privateKey == NULL)) {`
63. `return nil;`
64. `} else if (![privateKey isKindOfClass:[NSString class]]) {`
65. `return nil;`
66. `} else if ([privateKey length] <= 0) {`
67. `return nil;`
68. `}`
69. `//解析私钥对象内容`
70. `NSString *pKey = [NSString stringWithFormat:@"%@",privateKey];`
71. `NSRange sposition = [pKey rangeOfString:@"-----BEGIN RSA PRIVATE KEY-----"];`
72. `NSRange eposition = [pKey rangeOfString:@"-----END RSA PRIVATE KEY-----"];`
73. `if (sposition.location != NSNotFound && eposition.location != NSNotFound)`
74. `{`
75. `NSUInteger endposition = eposition.location;`
76. `NSUInteger startposition = sposition.location + sposition.length;`
77. `NSRange range = NSMakeRange(startposition, endposition-startposition);`
78. `pKey = [pKey substringWithRange:range];`
79. `}`
80. `pKey = [pKey stringByReplacingOccurrencesOfString:@"r" withString:@""];`
81. `pKey = [pKey stringByReplacingOccurrencesOfString:@"n" withString:@""];`
82. `pKey = [pKey stringByReplacingOccurrencesOfString:@"t" withString:@""];`
83. `pKey = [pKey stringByReplacingOccurrencesOfString:@" " withString:@""];`
84. `//This will be base64 encoded, decode it.`
85. `NSData *keyData = [Base64 base64DecodeDataWithString:pKey];`
86. `keyData = [self stripPrivateKeyHeader:keyData];`
87. `if ((keyData == nil) || (keyData == NULL)) {`
88. `return nil;`
89. `} else if (![keyData isKindOfClass:[NSData class]]) {`
90. `return nil;`
91. `} else if ([keyData length] <= 0) {`
92. `return nil;`
93. `}`
94. `//a tag to read/write keychain storage`
95. `NSString *tag = @"RSAUtil_PrivKey";`
96. `const void *bytes = [tag UTF8String];`
97. `NSData *tagData = [NSData dataWithBytes:bytes length:[tag length]];`
98. `//Delete any old lingering key with the same tag`
99. `NSMutableDictionary *attributes = [[NSMutableDictionary alloc] init];`
100. `[attributes setObject:(__bridge id)kSecClassKey`
101. `forKey:(__bridge id)kSecClass];`
102. `[attributes setObject:(__bridge id)kSecAttrKeyTypeRSA`
103. `forKey:(__bridge id)kSecAttrKeyType];`
104. `[attributes setObject:tagData`
105. `forKey:(__bridge id)kSecAttrApplicationTag];`
106. `SecItemDelete((__bridge CFDictionaryRef)attributes);`
107. `//Add persistent version of the key to system keychain`
108. `[attributes setObject:keyData forKey:(__bridge id)kSecValueData];`
109. `[attributes setObject:(__bridge id)kSecAttrKeyClassPrivate`
110. `forKey:(__bridge id)kSecAttrKeyClass];`
111. `[attributes setObject:[NSNumber numberWithBool:YES]`
112. `forKey:(__bridge id)kSecReturnPersistentRef];`
113. `OSStatus status = noErr;`
114. `CFTypeRef persistKey = nil;`
115. `status = SecItemAdd((__bridge CFDictionaryRef)attributes, &persistKey);`
116. `if (persistKey != nil) {CFRelease(persistKey);}`
117. `if ((status != noErr) && (status != errSecDuplicateItem))`
118. `{`
119. `return nil;`
120. `}`
121. `[attributes removeObjectForKey:(__bridge id)kSecValueData];`
122. `[attributes removeObjectForKey:(__bridge id)kSecReturnPersistentRef];`
123. `[attributes setObject:[NSNumber numberWithBool:YES]`
124. `forKey:(__bridge id)kSecReturnRef];`
125. `[attributes setObject:(__bridge id)kSecAttrKeyTypeRSA`
126. `forKey:(__bridge id)kSecAttrKeyType];`
127. `//Now fetch the SecKeyRef version of the key`
128. `SecKeyRef keyRef = nil;`
129. `CFDictionaryRef query = (__bridge CFDictionaryRef)attributes;`
130. `status = SecItemCopyMatching(query, (CFTypeRef *)&keyRef);`
131. `if (status != noErr)`
132. `{`
133. `return nil;`
134. `}`
135. `return keyRef;`
136. `}`
137. `+ (NSData *)stripPrivateKeyHeader:(NSData *)d_key`
138. `{`
139. `//Skip ASN.1 private key header`
140. `if (d_key == nil) return nil;`
141. `unsigned long len = [d_key length];`
142. `if (!len) return nil;`
143. `unsigned char *c_key = (unsigned char *)[d_key bytes];`
144. `unsigned int idx = 22; //magic byte at offset 22`
145. `if (0x04 != c_key[idx++]) return nil;`
146. `//calculate length of the key`
147. `unsigned int c_len = c_key[idx++];`
148. `if (!(c_len & 0x80))`
149. `{`
150. `c_len = c_len & 0x7f;`
151. `}`
152. `else`
153. `{`
154. `int byteCount = c_len & 0x7f;`
155. `if (byteCount + idx > len) {`
156. `//rsa length field longer than buffer`
157. `return nil;`
158. `}`
159. `unsigned int accum = 0;`
160. `unsigned char *ptr = &c_key[idx];`
161. `idx += byteCount;`
162. `while (byteCount) {`
163. `accum = (accum << 8) + *ptr;`
164. `ptr++;`
165. `byteCount--;`
166. `}`
167. `c_len = accum;`
168. `}`
169. `//Now make a new NSData from this buffer`
170. `return [d_key subdataWithRange:NSMakeRange(idx, c_len)];`
171. `}`
172. `+ (SecKeyRef)getPublicKeyRefWithFilePath:(NSString *)filePath`
173. `{`
174. `//读取公钥证书文件的内容`
175. `NSData *certificateData = [NSData dataWithContentsOfFile:filePath];`
176. `if ((certificateData == nil) || (certificateData == NULL)) {`
177. `return nil;`
178. `} else if (![certificateData isKindOfClass:[NSData class]]) {`
179. `return nil;`
180. `} else if ([certificateData length] <= 0) {`
181. `return nil;`
182. `}`
183. `//将公钥证书制作成证书对象`
184. `CFDataRef data = (__bridge CFDataRef)certificateData;`
185. `SecCertificateRef certificateRef = SecCertificateCreateWithData(NULL, data);`
186. `//获取公钥对象`
187. `SecTrustRef trust = NULL;`
188. `SecKeyRef publicKey = NULL;`
189. `SecPolicyRef policies = SecPolicyCreateBasicX509();`
190. `if (![[self class] isEmptyKeyRef:(__bridge id)(certificateRef)]`
191. `&& ![[self class] isEmptyKeyRef:(__bridge id)(policies)])`
192. `{`
193. `OSStatus status;`
194. `status = SecTrustCreateWithCertificates((CFTypeRef)certificateRef,`
195. `policies, &trust);`
196. `if (status == noErr)`
197. `{`
198. `SecTrustResultType result;`
199. `if (SecTrustEvaluate(trust, &result) == noErr)`
200. `{`
201. `publicKey = SecTrustCopyPublicKey(trust);`
202. `}`
203. `}`
204. `}`
205. `if (certificateRef != NULL) CFRelease(certificateRef);`
206. `if (policies != NULL) CFRelease(policies);`
207. `if (trust != NULL) CFRelease(trust);`
208. `return publicKey;`
209. `}`
210. `+ (SecKeyRef)publicKeyRefWithPublicKey:(NSString *)publicKey`
211. `{`
212. `//判断参数是否正确`
213. `if ((publicKey == nil) || (publicKey == NULL)) {`
214. `return nil;`
215. `} else if (![publicKey isKindOfClass:[NSString class]]) {`
216. `return nil;`
217. `} else if ([publicKey length] <= 0) {`
218. `return nil;`
219. `}`
220. `//解析公钥对象内容`
221. `NSString *pKey = [NSString stringWithFormat:@"%@",publicKey];`
222. `NSRange sposition = [pKey rangeOfString:@"-----BEGIN PUBLIC KEY-----"];`
223. `NSRange eposition = [pKey rangeOfString:@"-----END PUBLIC KEY-----"];`
224. `if (sposition.location != NSNotFound && eposition.location != NSNotFound)`
225. `{`
226. `NSUInteger startposition = eposition.location;`
227. `NSUInteger endposition = sposition.location + sposition.length;`
228. `NSRange range = NSMakeRange(endposition, startposition-endposition);`
229. `pKey = [pKey substringWithRange:range];`
230. `}`
231. `pKey = [pKey stringByReplacingOccurrencesOfString:@"r" withString:@""];`
232. `pKey = [pKey stringByReplacingOccurrencesOfString:@"n" withString:@""];`
233. `pKey = [pKey stringByReplacingOccurrencesOfString:@"t" withString:@""];`
234. `pKey = [pKey stringByReplacingOccurrencesOfString:@" " withString:@""];`
235. `//This will be base64 encoded, decode it.`
236. `NSData *keyData = [[self class] base64DecodeDataWithString:pKey];`
237. `keyData = [self stripPublicKeyHeader:keyData];`
238. `if ((keyData == nil) || (keyData == NULL)) {`
239. `return nil;`
240. `} else if (![keyData isKindOfClass:[NSData class]]) {`
241. `return nil;`
242. `} else if ([keyData length] <= 0) {`
243. `return nil;`
244. `}`
245. `//a tag to read/write keychain storage`
246. `NSString *tag = @"RSAUtil_PubKey";`
247. `const void *bytes = [tag UTF8String];`
248. `NSData *tagData = [NSData dataWithBytes:bytes length:[tag length]];`
249. `//Delete any old lingering key with the same tag`
250. `NSMutableDictionary *attributes = [[NSMutableDictionary alloc] init];`
251. `[attributes setObject:(__bridge id)kSecClassKey`
252. `forKey:(__bridge id)kSecClass];`
253. `[attributes setObject:(__bridge id)kSecAttrKeyTypeRSA`
254. `forKey:(__bridge id)kSecAttrKeyType];`
255. `[attributes setObject:tagData`
256. `forKey:(__bridge id)kSecAttrApplicationTag];`
257. `SecItemDelete((__bridge CFDictionaryRef)attributes);`
258. `//Add persistent version of the key to system keychain`
259. `[attributes setObject:keyData`
260. `forKey:(__bridge id)kSecValueData];`
261. `[attributes setObject:(__bridge id)kSecAttrKeyClassPublic`
262. `forKey:(__bridge id)kSecAttrKeyClass];`
263. `[attributes setObject:[NSNumber numberWithBool:YES]`
264. `forKey:(__bridge id)kSecReturnPersistentRef];`
265. `OSStatus status = noErr;`
266. `CFTypeRef persistKey = nil;`
267. `status = SecItemAdd((__bridge CFDictionaryRef)attributes, &persistKey);`
268. `if (persistKey != nil) CFRelease(persistKey);`
269. `if ((status != noErr) && (status != errSecDuplicateItem))`
270. `{`
271. `return nil;`
272. `}`
273. `[attributes removeObjectForKey:(__bridge id)kSecValueData];`
274. `[attributes removeObjectForKey:(__bridge id)kSecReturnPersistentRef];`
275. `[attributes setObject:[NSNumber numberWithBool:YES]`
276. `forKey:(__bridge id)kSecReturnRef];`
277. `[attributes setObject:(__bridge id)kSecAttrKeyTypeRSA`
278. `forKey:(__bridge id)kSecAttrKeyType];`
279. `//Now fetch the SecKeyRef version of the key`
280. `SecKeyRef publicKeyRef = nil;`
281. `CFDictionaryRef query = (__bridge CFDictionaryRef)attributes;`
282. `status = SecItemCopyMatching(query, (CFTypeRef *)&publicKeyRef);`
283. `if (status != noErr)`
284. `{`
285. `return nil;`
286. `}`
287. `return publicKeyRef;`
288. `}`
289. `+ (NSData *)stripPublicKeyHeader:(NSData *)d_key`
290. `{`
291. `//Skip ASN.1 public key header`
292. `if (d_key == nil) {return nil;}`
293. `unsigned long len = [d_key length];`
294. `if (!len) return(nil);`
295. `unsigned char *c_key = (unsigned char *)[d_key bytes];`
296. `unsigned int idx = 0;`
297. `if (c_key[idx++] != 0x30) {return nil;}`
298. `if (c_key[idx] > 0x80)`
299. `{`
300. `idx += c_key[idx] - 0x80 + 1;`
301. `}`
302. `else`
303. `{`
304. `idx++;`
305. `}`
306. `//PKCS #1 rsaEncryption szOID_RSA_RSA`
307. `static unsigned char seqiod[] = {0x30, 0x0d, 0x06, 0x09, 0x2a,`
308. `0x86, 0x48, 0x86, 0xf7, 0x0d,`
309. `0x01, 0x01, 0x01, 0x05, 0x00};`
310. `if (memcmp(&c_key[idx], seqiod, 15)) {return nil;}`
311. `idx += 15;`
312. `if (c_key[idx++] != 0x03) {return nil;}`
313. `if (c_key[idx] > 0x80)`
314. `{`
315. `idx += c_key[idx] - 0x80 + 1;`
316. `}`
317. `else`
318. `{`
319. `idx ++;`
320. `}`
321. `if (c_key[idx++] != '') {return nil;}`
322. `//Now make a new NSData from this buffer`
323. `return ([NSData dataWithBytes:&c_key[idx] length:len - idx]);`
324. `}`
325. `+ (NSData *)encryptData:(NSData *)data withKeyRef:(SecKeyRef)keyRef`
326. `{`
327. `const uint8_t *srcbuf = (const uint8_t *)[data bytes];`
328. `size_t srclen = (size_t)data.length;`
329. `size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);`
330. `void *outbuf = malloc(block_size);`
331. `size_t src_block_size = block_size - 11;`
332. `NSMutableData *ret = [[NSMutableData alloc] init];`
333. `for (int idx = 0; idx < srclen; idx += src_block_size)`
334. `{`
335. `size_t data_len = srclen - idx;`
336. `if(data_len > src_block_size){`
337. `data_len = src_block_size;`
338. `}`
339. `size_t outlen = block_size;`
340. `OSStatus status = noErr;`
341. `status = SecKeyEncrypt(keyRef, kSecPaddingPKCS1,`
342. `srcbuf + idx, data_len,`
343. `outbuf, &outlen);`
344. `if (status != 0)`
345. `{`
346. `NSLog(@"SecKeyEncrypt fail. Error Code: %d", (int)status);`
347. `ret = nil;`
348. `break;`
349. `}`
350. `else`
351. `{`
352. `[ret appendBytes:outbuf length:outlen];`
353. `}`
354. `}`
355. `free(outbuf);`
356. `CFRelease(keyRef);`
357. `return ret;`
358. `}`
359. `+ (NSData *)decryptData:(NSData *)data withKeyRef:(SecKeyRef)keyRef`
360. `{`
361. `const uint8_t *srcbuf = (const uint8_t *)[data bytes];`
362. `size_t srclen = (size_t)data.length;`
363. `size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);`
364. `UInt8 *outbuf = malloc(block_size);`
365. `size_t src_block_size = block_size;`
366. `NSMutableData *ret = [[NSMutableData alloc] init];`
367. `for (int idx = 0; idx < srclen; idx += src_block_size)`
368. `{`
369. `size_t data_len = srclen - idx;`
370. `if(data_len > src_block_size)`
371. `{`
372. `data_len = src_block_size;`
373. `}`
374. `size_t outlen = block_size;`
375. `OSStatus status = noErr;`
376. `status = SecKeyDecrypt(keyRef, kSecPaddingNone,`
377. `srcbuf + idx, data_len,`
378. `outbuf, &outlen);`
379. `if (status != 0)`
380. `{`
381. `NSLog(@"SecKeyEncrypt fail. Error Code: %d", (int)status);`
382. `ret = nil;`
383. `break;`
384. `}`
385. `else`
386. `{`
387. `int idxFirstZero = -1;`
388. `int idxNextZero = (int)outlen;`
389. `for (int i = 0; i < outlen; i ++)`
390. `{`
391. `if (outbuf[i] == 0)`
392. `{`
393. `if (idxFirstZero < 0)`
394. `{`
395. `idxFirstZero = i;`
396. `}`
397. `else`
398. `{`
399. `idxNextZero = i;`
400. `break;`
401. `}`
402. `}`
403. `}`
404. `NSUInteger length = idxNextZero-idxFirstZero-1;`
405. `[ret appendBytes:&outbuf[idxFirstZero+1] length:length];`
406. `}`
407. `}`
408. `free(outbuf);`
409. `CFRelease(keyRef);`
410. `return ret;`
411. `}`
412. `pragma mark - RSA Key File Encrypt/Decrypt Public Method`
413. `+ (NSString *)encryptString:(NSString *)originString publicKeyPath:(NSString *)publicKeyPath`
414. `{`
415. `//判断originString参数是否正确`
416. `if ((originString == nil) || (originString == NULL)) {`
417. `return nil;`
418. `} else if (![originString isKindOfClass:[NSString class]]) {`
419. `return nil;`
420. `} else if ([originString length] <= 0) {`
421. `return nil;`
422. `}`
423. `//判断publicKeyPath参数是否正确`
424. `if ((publicKeyPath == nil) || (publicKeyPath == NULL)) {`
425. `return nil;`
426. `} else if (![publicKeyPath isKindOfClass:[NSString class]]) {`
427. `return nil;`
428. `} else if ([publicKeyPath length] <= 0) {`
429. `return nil;`
430. `}`
431. `//获取公钥对象和需要加密的字符串内容编码数据流`
432. `SecKeyRef publicKeyRef = [self getPublicKeyRefWithFilePath:publicKeyPath];`
433. `NSData *originData = [originString dataUsingEncoding:NSUTF8StringEncoding];`
434. `if ([[self class] isEmptyKeyRef:(__bridge id)(publicKeyRef)]) {`
435. `return nil;`
436. `}`
437. `if ((originData == nil) || (originData == NULL)) {`
438. `return nil;`
439. `} else if (![originData isKindOfClass:[NSData class]]) {`
440. `return nil;`
441. `} else if ([originData length] <= 0) {`
442. `return nil;`
443. `}`
444. `//加密源字符串内容编码数据流的数据`
445. `NSData *resultData = nil;`
446. `resultData = [self encryptData:originData withKeyRef:publicKeyRef];`
447. `return [[self class] base64EncodedStringWithData:resultData];`
448. `}`
449. `+ (NSString *)decryptString:(NSString *)encryptString privateKeyPath:(NSString *)privateKeyPath privateKeyPwd:(NSString *)privateKeyPwd`
450. `{`
451. `//判断encryptString参数是否正确`
452. `if ((encryptString == nil) || (encryptString == NULL)) {`
453. `return nil;`
454. `} else if (![encryptString isKindOfClass:[NSString class]]) {`
455. `return nil;`
456. `} else if ([encryptString length] <= 0) {`
457. `return nil;`
458. `}`
459. `//判断publicKeyPath参数是否正确`
460. `if ((privateKeyPath == nil) || (privateKeyPath == NULL)) {`
461. `return nil;`
462. `} else if (![privateKeyPath isKindOfClass:[NSString class]]) {`
463. `return nil;`
464. `} else if ([privateKeyPath length] <= 0) {`
465. `return nil;`
466. `}`
467. `//判断密码是否存在`
468. `NSString *keyPassword = [NSString stringWithFormat:@"%@",privateKeyPwd];`
469. `if ((privateKeyPwd == nil) || (privateKeyPwd == NULL)) {`
470. `keyPassword = @"";`
471. `} else if (![privateKeyPwd isKindOfClass:[NSString class]]) {`
472. `keyPassword = @"";`
473. `} else if ([privateKeyPwd length] <= 0) {`
474. `keyPassword = @"";`
475. `}`
476. `//获取私钥对象和需要加密的字符串内容编码数据流`
477. `NSData *encryptData = nil, *decryptData = nil;`
478. `SecKeyRef privateKeyRef = [self getPrivateKeyRefWithFilePath:privateKeyPath`
479. `keyPassword:privateKeyPwd];`
480. `encryptData = [[self class] base64DecodeDataWithString:encryptString];`
481. `if ([[self class] isEmptyKeyRef:(__bridge id)(privateKeyRef)]) {`
482. `return nil;`
483. `}`
484. `if ((encryptData == nil) || (encryptData == NULL)) {`
485. `return nil;`
486. `} else if (![encryptData isKindOfClass:[NSData class]]) {`
487. `return nil;`
488. `} else if ([encryptData length] <= 0) {`
489. `return nil;`
490. `}`
491. `NSStringEncoding encoding = NSUTF8StringEncoding;`
492. `decryptData = [self decryptData:encryptData withKeyRef:privateKeyRef];`
493. `return [[NSString alloc] initWithData:decryptData encoding:encoding];`
494. `}`
495. `pragma mark - RSA Key String Encrypt/Decrypt Public Method`
496. `+ (NSData *)encryptData:(NSData *)originData publicKey:(NSString *)publicKey`
497. `{`
498. `//判断originData参数是否正确`
499. `if ((originData == nil) || (originData == NULL)) {`
500. `return nil;`
501. `} else if (![originData isKindOfClass:[NSData class]]) {`
502. `return nil;`
503. `} else if ([originData length] <= 0) {`
504. `return nil;`
505. `}`
506. `//判断publicKeyPath参数是否正确`
507. `if ((publicKey == nil) || (publicKey == NULL)) {`
508. `return nil;`
509. `} else if (![publicKey isKindOfClass:[NSString class]]) {`
510. `return nil;`
511. `} else if ([publicKey length] <= 0) {`
512. `return nil;`
513. `}`
514. `//获取需要加密的字符串内容编码数据流`
515. `SecKeyRef publicKeyRef = [self publicKeyRefWithPublicKey:publicKey];`
516. `if([[self class] isEmptyKeyRef:(__bridge id)(publicKeyRef)]){`
517. `return nil;`
518. `}`
519. `return [self encryptData:originData withKeyRef:publicKeyRef];`
520. `}`
521. `+ (NSString *)encryptString:(NSString *)originString publicKey:(NSString *)publicKey`
522. `{`
523. `//判断publicKey参数是否正确`
524. `if ((publicKey == nil) || (publicKey == NULL)) {`
525. `return nil;`
526. `} else if (![publicKey isKindOfClass:[NSString class]]) {`
527. `return nil;`
528. `} else if ([publicKey length] <= 0) {`
529. `return nil;`
530. `}`
531. `//判断originString参数是否正确`
532. `if ((originString == nil) || (originString == NULL)) {`
533. `return nil;`
534. `} else if (![originString isKindOfClass:[NSString class]]) {`
535. `return nil;`
536. `} else if ([originString length] <= 0) {`
537. `return nil;`
538. `}`
539. `//获取需要加密的字符串内容编码数据流`
540. `NSData *originData = nil, *encryptData = nil;`
541. `SecKeyRef publicKeyRef = [self publicKeyRefWithPublicKey:publicKey];`
542. `originData = [originString dataUsingEncoding:NSUTF8StringEncoding];`
543. `if([[self class] isEmptyKeyRef:(__bridge id)(publicKeyRef)]){`
544. `return nil;`
545. `}`
546. `if ((originData == nil) || (originData == NULL)) {`
547. `return nil;`
548. `} else if (![originData isKindOfClass:[NSData class]]) {`
549. `return nil;`
550. `} else if ([originData length] <= 0) {`
551. `return nil;`
552. `}`
553. `encryptData = [self encryptData:originData withKeyRef:publicKeyRef];`
554. `return [[self class] base64EncodedStringWithData:encryptData];`
555. `}`
556. `+ (NSString *)decryptString:(NSString *)encryptString privateKey:(NSString *)privateKey`
557. `{`
558. `//判断publicKey参数是否正确`
559. `if ((privateKey == nil) || (privateKey == NULL)) {`
560. `return nil;`
561. `} else if (![privateKey isKindOfClass:[NSString class]]) {`
562. `return nil;`
563. `} else if ([privateKey length] <= 0) {`
564. `return nil;`
565. `}`
566. `//判断originString参数是否正确`
567. `if ((encryptString == nil) || (encryptString == NULL)) {`
568. `return nil;`
569. `} else if (![encryptString isKindOfClass:[NSString class]]) {`
570. `return nil;`
571. `} else if ([encryptString length] <= 0) {`
572. `return nil;`
573. `}`
574. `//获取私钥对象和需要加密的字符串内容编码数据流`
575. `SecKeyRef privateKeyRef;`
576. `NSData *encryptData = nil, *decryptData = nil;`
577. `privateKeyRef = [[self class] privateKeyRefWithPrivateKey:privateKey];`
578. `encryptData = [[self class] base64DecodeDataWithString:encryptString];`
579. `if ([[self class] isEmptyKeyRef:(__bridge id)(privateKeyRef)]) {`
580. `return nil;`
581. `}`
582. `if ((encryptData == nil) || (encryptData == NULL)) {`
583. `return nil;`
584. `} else if (![encryptData isKindOfClass:[NSData class]]) {`
585. `return nil;`
586. `} else if ([encryptData length] <= 0) {`
587. `return nil;`
588. `}`
589. `NSStringEncoding encoding = NSUTF8StringEncoding;`
590. `decryptData = [self decryptData:encryptData withKeyRef:privateKeyRef];`
591. `return [[NSString alloc] initWithData:decryptData encoding:encoding];`
592. `}`
593. `/******************************************************************************/`
在iOS中RSA加解密使用方法介绍（RSA密钥格式请使用PKCS#8格式）
1. `//使用RSA执行加密操作`
2. `NSString *string4 = @"abcdefghijklmnopqrstuvwxyz";`
3. `NSString *encodeString4 = [RSAEncrypt encryptString:string4`
4. `publicKey:mPublicKey];`
5. `NSLog(@"encodeString4 : %@", encodeString4);`
6. `//使用RSA执行解密操作`
7. `NSString *decodeString4 = [RSAEncrypt decryptString:encodeString4`
8. `privateKey:mPrivateKey];`
9. `NSLog(@"decodeString4 : %@", decodeString4);`
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