iOS 上的 RSA 加密方法
作者链接：http://johnny.logdown.com/posts/69881-rsa-encryption-method-on-ios
由於工作上需要，最近在研究 iOS 上的 RSA 加密/解密，網路上的文章實在少之又少，下了一番苦工之後，終於讓我找齊資料成功在iOS上用 RSA 來加密/解密字串!不過不是自己寫出來的，我要是有這麼神就好了 XD這篇文章主要是把網路上的資料蒐集起來，讓有需要的人可以快速上手，真正還是要感謝寫出這些 code 的神人 (對我來說啦..||)文末也會附上資料來源，希望這篇文章對你有幫助 :)RSA加密方法簡單的說就是有一組 公鑰(Public Key) 還有一組 私鑰(Private Key)私鑰拿來解密，公鑰則拿來加密用。所以我們來產生一組公鑰跟私鑰吧! 打開你的 Terminal，輸入以下指令cd Desktopopenssl req -x509 -out public_key.der -outform der -new -newkey rsa:2048 -keyout private_key.pem days 3650 -nodes產生公鑰私鑰的過程中會要你輸入一些資訊，可填可不填，應該是不會有什麼影響如果沒問題的話，你的桌面上現在應該會產生兩個檔案：public_key.der 還有 private_key.pem，這兩個分別是我們的公鑰和私鑰。接下來是加密用的 Class，如何在Xcode新增新的Class就不在此冗述了，以下是代碼：使用前必須先導入 Security.framework，並且把你剛剛產生的 publickey.der 新增到你的 Project 裡面。
RSAEncrypt.h
#import@interface RSAEncrypt : NSObject {
SecKeyRef publicKey;
SecCertificateRef certificate;
SecPolicyRef policy;
SecTrustRef trust;
size_t maxPlainLen;
}
- (NSData *) encryptWithData:(NSData *)content;
- (NSData *) encryptWithString:(NSString *)content;
- (NSString *) encryptToString:(NSString *)content;
@end
RSAEncrypt.m
#import "RSAEncrypt.h"
@implementation RSAEncrypt
- (id)init {
self = [super init];
NSString *publicKeyPath = [[NSBundle mainBundle] pathForResource:@"public_key" ofType:@"der"];
//從檔案讀取公鑰
if (publicKeyPath == nil) {
NSLog(@"Can not find pub.der");
return nil;
}
NSDate *publicKeyFileContent = [NSData dataWithContentsOfFile:publicKeyPath];
if (publicKeyFileContent == nil) {
NSLog(@"Can not read from pub.der");
return nil;
}
certificate = SecCertificateCreateWithData(kCFAllocatorDefault, ( __bridge CFDataRef)publicKeyFileContent);
if (certificate == nil) {
NSLog(@"Can not read certificate from pub.der");
return nil;
}
policy = SecPolicyCreateBasicX509();
OSStatus returnCode = SecTrustCreateWithCertificates(certificate, policy, &trust);
if (returnCode != 0) {
NSLog(@"SecTrustCreateWithCertificates fail. Error Code: %ld", returnCode);
return nil;
}
SecTrustResultType trustResultType;
returnCode = SecTrustEvaluate(trust, &trustResultType);
if (returnCode != 0) {
return nil;
}
publicKey = SecTrustCopyPublicKey(trust);
if (publicKey == nil) {
NSLog(@"SecTrustCopyPublicKey fail");
return nil;
}
maxPlainLen = SecKeyGetBlockSize(publicKey) - 12;
return self;
}
- (NSData *) encryptWithData:(NSData *)content {
size_t plainLen = [content length];
if (plainLen > maxPlainLen) {
NSLog(@"content(%ld) is too long, must < %ld", plainLen, maxPlainLen);
return nil;
}
void *plain = malloc(plainLen);
[content getBytes:plain
length:plainLen];
size_t cipherLen = 256; // 目前使用的RSA加密長度為2048bits(即256bytes)
void *cipher = malloc(cipherLen);
OSStatus returnCode = SecKeyEncrypt(publicKey, kSecPaddingPKCS1, plain,
plainLen, cipher, &cipherLen);
NSData *result = nil;
if (returnCode != 0) {
NSLog(@"SecKeyEncrypt fail. Error Code: %ld", returnCode);
}
else {
result = [NSData dataWithBytes:cipher length:cipherLen];
}
free(plain);
free(cipher);
return result;
}
- (NSData *) encryptWithString:(NSString *)content {
return [self encryptWithData:[content dataUsingEncoding:NSUTF8StringEncoding]];
}
- (NSString *) encryptToString:(NSString *)content {
NSData *data = [self encryptWithString:content];
return [self base64forData:data];
}
// convert NSData to NSString
- (NSString *)base64forData:(NSData *)theData {
const uint8_t* input = (const uint8_t*)[theData bytes];
NSInteger length = [theData length];
static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
NSMutableData* data = [NSMutableData dataWithLength:((length + 2) / 3) * 4];
uint8_t* output = (uint8_t*)data.mutableBytes;
NSInteger i;
for (i=0; i < length; i += 3) {
NSInteger value = 0;
NSInteger j;
for (j = i; j < (i + 3); j++) {
value <<= 8;
if (j < length) {
value |= (0xFF & input[j]);
}
}
NSInteger theIndex = (i / 3) * 4;
output[theIndex + 0] = table[(value >> 18) & 0x3F];
output[theIndex + 1] = table[(value >> 12) & 0x3F];
output[theIndex + 2] = (i + 1) < length ? table[(value >> 6) & 0x3F] : '=';
output[theIndex + 3] = (i + 2) < length ? table[(value >> 0) & 0x3F] : '=';
}
return [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
}
- (void)dealloc{
CFRelease(certificate);
CFRelease(trust);
CFRelease(policy);
CFRelease(publicKey);
}
@end
加密字串
RSAEncrypt *rsa = [[RSAEncrypt alloc] init];
if (rsa != nil) {
NSString *string = [rsa encryptToString:@"Hello Objective-C"]
} else {
NSLog(@"Error");
}
string 即可得RSA加密後的字串。
還有其他兩個方法可以使用，就讓大家自己去發掘啦 XD
- (NSData *) encryptWithData:(NSData *)content;
- (NSData *) encryptWithString:(NSString *)content;
Reference
http://zh.wikipedia.org/zh-tw/RSA%E5%8A%A0%E5%AF%86%E6%BC%94%E7%AE%97%E6%B3%95
http://blog.iamzsx.me/show.html?id=155002
