SEED 블록암호 알고리즘 CBC (Cipher Block Chaining) 예제 (2/2)

최근 SEED 블록 암호 알고리즘 CBC 암복호화 처리를

해야할 일이 생겨 관련 클래스를 제작하게 되었습니다

혹시 같은 작업을 하시는분에게 도움이 되었으면 합니다.

아래 작업은 Swift프로젝트에서 작업되었습니다.

 

SEED 블록암호 알고리즘

seed.kisa.or.kr/kisa/Board/17/detailView.do

KISA 암호이용활성화 - 암호알고리즘 소스코드

 

KISA_SEED_CBC.h

다음 함수를 헤더에 선언해 주도록 한다.

extern int encryptSeedCBC( IN BYTE *pbszUserKey, IN BYTE *pbszIV, IN BYTE *pbszPlainText, OUT BYTE *pbszCipherText );
extern int decryptSeedCBC( IN BYTE *pbszUserKey, IN BYTE *pbszIV, IN BYTE *pbszCipherText, OUT BYTE *pbszPlainText );

 

KISA_SEED_CBC.c

다음과 같이 작성해 준다.

작성에 앞서 main()함수는 제거해주도록 하자.

int encryptSeedCBC( IN BYTE *pbszUserKey, IN BYTE *pbszIV, IN BYTE *pbszPlainText, OUT BYTE *pbszCipherText )
{
    printf("\n---------------------------------");
    printf("\nplainText : %s\n", (char *)pbszPlainText);
    
    int nPlainTextLen = (int)strlen((char *)pbszPlainText);// 평문의 Byte길이
    printf ("\n---------------------------------");
    printf ("\nSEED CBC Encryption....\n");
    // 암호문의 Byte길이 - 패딩 로직때문에 16바이트 블럭으로 처리함으로 pbszCipherText는 평문보다 16바이트 커야 한다.
    int nCipherTextLen = SEED_CBC_Encrypt( pbszUserKey, pbszIV, pbszPlainText, nPlainTextLen, pbszCipherText );
    return nCipherTextLen;
}

int decryptSeedCBC( IN BYTE *pbszUserKey, IN BYTE *pbszIV, IN BYTE *pbszCipherText, OUT BYTE *pbszPlainText )
{
    int nCipherTextLen = (int)strlen((char *)pbszCipherText);// 암호문의 Byte길이
    printf ("\n---------------------------------");
    printf ("\nSEED CBC Decryption....\n");
    // 평문의 Byte길이
    int nPlainTextLen = SEED_CBC_Decrypt( pbszUserKey, pbszIV, pbszCipherText, nCipherTextLen, pbszPlainText );
    return nPlainTextLen;
}

 

CryptoUtil  유틸 클래스 생성

//
//  CryptoUtil.h
//  
//
//  Created by netcanis on 2020/07/09.
//  Copyright © 2020 netcanis. All rights reserved.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface CryptoUtil : NSObject

+(NSString *)encrypt:(NSString *)masterKey msg:(NSString *)msg;
+(NSString *)encrypt:(Byte *)key iv:(Byte *)iv msg:(NSString *)msg;

+(NSString *)decrypt:(NSString *)masterKey msg:(NSString *)base64Str;
+(NSString *)decrypt:(Byte *)key iv:(Byte *)iv msg:(NSString *)base64Str;

+(NSData *)getSHA256:(NSString *)msg;
+(NSString *)hash:(NSString *)secret payload:(NSString *)payload;

@end

NS_ASSUME_NONNULL_END

 

//
//  CryptoUtil.m
//  
//
//  Created by netcanis on 2020/07/09.
//  Copyright © 2020 netcanis. All rights reserved.
//

#import "CryptoUtil.h"
#import "CocoaSecurity.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "KISA_SEED_CBC.h"


@implementation CryptoUtil



+(NSString *)encrypt:(NSString *)masterKey msg:(NSString *)msg {
    NSData *sha256 = [self getSHA256:masterKey];
    NSData *key = [sha256 subdataWithRange:NSMakeRange(0, 16)];
    NSData *iv = [sha256 subdataWithRange:NSMakeRange(16, 16)];
    
    BYTE pbszPlainText[2048] = {0,};
    memset(pbszPlainText, 0, [msg length]);
    const char *byteBuff = [msg UTF8String];
    memcpy(pbszPlainText, (BYTE *)byteBuff, strlen(byteBuff));
    
    // 암호문 출력 버퍼
    BYTE pbszCipherText[2048] = {0,};
    int nCipherTextLen = encryptSeedCBC( (BYTE *)[key bytes], (BYTE *)[iv bytes], pbszPlainText, pbszCipherText );

    // base64 encode
    NSData *data = [[NSData alloc] initWithBytes:pbszCipherText length:nCipherTextLen];
    NSString *base64String = [data base64EncodedStringWithOptions:0];

    // memory clean
    memset(pbszPlainText, 0, nCipherTextLen);
    memset((void *)[data bytes], 0, [data length]);

#ifdef DEBUG
    // log
    [CryptoUtil printHexaLog:pbszCipherText length:nCipherTextLen];
#endif//DEBUG
    
    return base64String;
}

+(NSString *)encrypt:(Byte *)key iv:(Byte *)iv msg:(NSString *)msg {
    
    BYTE pbszPlainText[2048] = {0,};
    memset(pbszPlainText, 0, [msg length]);
    const char *byteBuff = [msg UTF8String];
    memcpy(pbszPlainText, (BYTE *)byteBuff, strlen(byteBuff));
    
    // 암호문 출력 버퍼
    BYTE pbszCipherText[2048] = {0,};
    int nCipherTextLen = encryptSeedCBC( key, iv, pbszPlainText, pbszCipherText );

    // base64 encode
    NSData *data = [[NSData alloc] initWithBytes:pbszCipherText length:nCipherTextLen];
    NSString *base64String = [data base64EncodedStringWithOptions:0];

    // memory clean
    memset(pbszPlainText, 0, nCipherTextLen);
    memset((void *)[data bytes], 0, [data length]);
    
#ifdef DEBUG
    // log
    [CryptoUtil printHexaLog:pbszCipherText length:nCipherTextLen];
#endif//DEBUG
    
    return base64String;
}

+(NSString *)decrypt:(NSString *)masterKey msg:(NSString *)base64Str {
    NSData *sha256 = [self getSHA256:masterKey];
    NSData *key = [sha256 subdataWithRange:NSMakeRange(0, 16)];
    NSData *iv = [sha256 subdataWithRange:NSMakeRange(16, 16)];
    
    // base64 decode
    NSData *data = [[NSData alloc] initWithBase64EncodedString:base64Str options:0];

    BYTE pbszCipherText[2048] = {0,};
    memcpy(pbszCipherText, [data bytes], [data length]);

    // 사용자 입력 평문
    BYTE pbszPlainText[2048] = {0,};
    int nPlainTextLen = decryptSeedCBC( (BYTE *)[key bytes], (BYTE *)[iv bytes], pbszCipherText, pbszPlainText );

    NSString *plainText = [[NSString alloc] initWithBytes:pbszPlainText length:nPlainTextLen encoding:NSUTF8StringEncoding];

    // memory clean
    memset(pbszCipherText, 0, nPlainTextLen);

#ifdef DEBUG
    // log
    [CryptoUtil printHexaLog:pbszPlainText length:nPlainTextLen];
#endif//DEBUG
    
    return plainText;
}

+(NSString *)decrypt:(Byte *)key iv:(Byte *)iv msg:(NSString *)base64Str {
    
    // base64 decode
    NSData *data = [[NSData alloc] initWithBase64EncodedString:base64Str options:0];

    BYTE pbszCipherText[2048] = {0,};
    memcpy(pbszCipherText, [data bytes], [data length]);

    // 사용자 입력 평문
    BYTE pbszPlainText[2048] = {0,};
    int nPlainTextLen = decryptSeedCBC( key, iv, pbszCipherText, pbszPlainText );

    NSString *plainText = [[NSString alloc] initWithBytes:pbszPlainText length:nPlainTextLen encoding:NSUTF8StringEncoding];

    // memory clean
    memset(pbszCipherText, 0, nPlainTextLen);
    
#ifdef DEBUG
    // log
    [CryptoUtil printHexaLog:pbszPlainText length:nPlainTextLen];
#endif//DEBUG
    
    return plainText;
}

+(NSData *)getSHA256:(NSString *)msg {
    NSData *data = [CocoaSecurity sha256:msg].data;
    return data;
}

+(NSString *)hash:(NSString *)secret payload:(NSString *)payload {
    NSString *result = [CocoaSecurity hmacSha256:payload hmacKey:secret].base64;
    return result;
}


+(void)printHexaLog:(BYTE *)pbBytes length:(NSInteger)length {
    printf ("\nLength (%ld)  : ", (long)length);
    for (int i=0;i<length;i++) {
        printf("%02X ",pbBytes[i]);
    }
}

@end

 

암호화 처리를 위해 CocoaSecurity 클래스를 사용했다.

https://github.com/kelp404/CocoaSecurity/tree/master/CocoaSecurity

kelp404/CocoaSecurity

 

해당 클래스도 프로젝트에 추가해 준다.

 

[ 사용방법 ] 

// encode
let msg = "2020070917085299920190520000001abcdefghijklmn"
let masterKey = "1234567890";
let enc = CryptoUtil.encrypt(masterKey, msg: msg)
print("\(enc)")

// output :
3JomiSXGgIuC6vbFELbIa3+5QyJlpv6cFgy6JDcPmRryk2V+y2sueCivAymkra6D


// decode
let dec = CryptoUtil.decrypt(masterKey, msg: enc)

// output :
2020070917085299920190520000001abcdefghijklmn

 

 

2020/07/11 - [분류 전체보기] - SEED 블록암호 알고리즘 CBC (Cipher Block Chaining) 예제2

2020/07/11 - [Android/Java] - Webview에서 새로운창 출력

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2020/07/11 - [Android/Kotlin] - byte array to hex string

2020/07/11 - [Android/Tips] - Android API Level 및 명칭

2020/07/11 - [Android/Tips] - ERROR: Could not get unknown property 'com' for root project 'myApp' of type org.gradle.api.Project

2020/07/11 - [Android/Tips] - error: cannot find symbol this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);

2020/07/11 - [Android/Rooting] - LG 펌웨어 추출 및 OS 다운그레이드 (kdz file)

2020/07/11 - [Android/Rooting] - 안드로이드 Fridump 환경설정 (4/4)

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2020/06/16 - [OS/Mac OS X] - duplicate symbol 에러 해결

2020/06/12 - [iOS/Jailbreak] - Fridump 사용법 (4/4) - 결과물 바이너리 검색

2020/06/03 - [iOS/Objective-C] - NSString <-> CBUUID