转自  http://www.jianshu.com/p/74a796ec5038  

 

 

在iOS中使用RSA加密解密，需要用到.der和.p12后缀格式的文件，其中.der格式的文件存放的是公钥（Public key）用于加密，.p12格式的文件存放的是私钥（Private key）用于解密. 首先需要先生成这些文件，然后再将文件导入工程使用，不多说，开始做！

一、使用openssl生成所需秘钥文件

　　生成环境是在mac系统下，使用openssl进行生成，首先打开终端，按下面这些步骤依次来做：

1. 生成模长为1024bit的私钥文件private_key.pem

openssl genrsa -out private_key.pem 1024

2. 生成证书请求文件rsaCertReq.csr

openssl req -new -key private_key.pem -out rsaCerReq.csr

注意：这一步会提示输入国家、省份、mail等信息，可以根据实际情况填写，或者全部不用填写，直接全部敲回车.

3. 生成证书rsaCert.crt，并设置有效时间为1年

openssl x509 -req -days 3650 -in rsaCerReq.csr -signkey private_key.pem -out rsaCert.crt

4. 生成供iOS使用的公钥文件public_key.der

openssl x509 -outform der -in rsaCert.crt -out public_key.der

5. 生成供iOS使用的私钥文件private_key.p12

openssl pkcs12 -export -out private_key.p12 -inkey private_key.pem -in rsaCert.crt

注意：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，完毕！

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.

6. 生成供Java使用的公钥rsa_public_key.pem

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

7. 生成供Java使用的私钥pkcs8_private_key.pem

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

全部执行成功后，会生成如下文件，其中public_key.der和private_key.p12就是iOS需要用到的文件，如下图：

生成的文件

二、将文件导入工程使用

1.新建工程, 并导入Security.framework框架, 如下图:

新建工程并添加框架

2.导入秘钥文件

导入.der和.p12格式的秘钥文件, 如下图:

导入秘钥文件

3.新建用于加密、解密的类RSAEncryptor, 并实现相关方法

新建RSAEncryptor类, 如下图:

新建用于加密解密的类

下面开始上代码, 可以直接复制过去用:

RSAEncryptor.h代码如下:

#import 
    
     @interface RSAEncryptor : NSObject /** * 加密方法 * * @param str 需要加密的字符串 * @param path '.der'格式的公钥文件路径 */ + (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; @end
    

RSAEncryptor.m代码如下:

#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] -