RSA加密

算法简介

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(e2*e1)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，设A为明文，B为密文，则：A=B^e2 mod n；B=A^e1 mod n；（公钥加密体制中，一般用公钥加密，私钥解密）
e1和e2可以互换使用，即：
A=B^e1 mod n；B=A^e2 mod n;

开发步骤

1.生成秘钥

1. 生成私密秘钥1024位的私钥

   openssl genrsa -out private.pem 1024

2. 利用私钥生成公钥
   openssl rsa -in private_key.pem -out rsa_public_key.pem -pubout

3. 生成请求生成证书dea文件

openssl req -new -key private.pem -out rsaCertReq.csr

4. 生成签名证书

openssl x509 -req -days 3650 -in rsaCertReq.csr -signkey private.pem -out rsaCert.crt

5.生成苹果需要的der证书
openssl x509 -outform der -in rsaCert.crt -out public_key.der
6. 生成p12文件

openssl pkcs12 -export -out private_key.p12 -inkey private.pem -in rsaCert.crt
期间要输入密码，这个密码一定要记住

也可以用下面的代码生成.sh文件进行执行即可

#!/usr/bin/env bashecho "Generating RSA key pair ..."echo "1024 RSA key: private_key.pem"openssl genrsa -out private_key.pem 1024echo "create certification require file: rsaCertReq.csr"openssl req -new -key private_key.pem -out rsaCertReq.csrecho "create certification using x509: rsaCert.crt"openssl x509 -req -days 3650 -in rsaCertReq.csr -signkey private_key.pem -out rsaCert.crtecho "create public_key.der For IOS"openssl x509 -outform der -in rsaCert.crt -out public_key.derecho "create private_key.p12 For IOS. Please remember your password. The password will be used in iOS."openssl pkcs12 -export -out private_key.p12 -inkey private_key.pem -in rsaCert.crtecho "create rsa_public_key.pem For Java"openssl rsa -in private_key.pem -out rsa_public_key.pem -puboutecho "create pkcs8_private_key.pem For Java"openssl pkcs8 -topk8 -in private_key.pem -out pkcs8_private_key.pem -nocryptecho "finished."

2.加密解密工具类

头文件

#import <Foundation/Foundation.h>@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;

体文件

#import "RSAEncryptor.h"#import <Security/Security.h>@implementation RSAEncryptorstatic 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<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 */@end

3.使用方法

加密

    NSString *filePath =  [[NSBundle mainBundle] pathForResource:@"public_key" ofType:@"der"];    //加密   NSString* result = [RSAEncryptor encryptString:@"加密数据" publicKeyWithContentsOfFile:filePath];

在iOS下解码需要先加载private key, 之后在对数据解码. 解码的时候先进行Base64 decode, 之后在用private key decrypt加密数据.

NSString *filePath =  [[NSBundle mainBundle] pathForResource:@"private_key" ofType:@"p12"];    NSString *decryptedString = [RSAEncryptor decryptString:@"密文" privateKeyWithContentsOfFile:filePath password:@"密码"];    NSLog(@"decrypted data: %@", decryptedString);

PS

由于非对称加密很慢，一般不用非对称加密而是
RSA + AES 组合（非对称 + 对称组合）
1.利用AES对称 对数据本身加密
2.RSA非对称算法，对AES的KEY加密