Re: decrypting a string

[system PRIVILEGED account]

Hi Dr S N Henson,
Thanks for your quick response. Please see following two C programs.
We really appreciate your help.

--Wanda Zeng--


/* 
 *      crypt.c 
 *
 *      encrypt a string
 *
 */

#include <stdio.h> 
#include <string.h> 
#include <openssl/evp.h>

main()
{
        char dev_query[]="query180900";
        char s[]="399";
        int i;

        unsigned char outstring1[1024];
        unsigned char key[8];  
        FILE    *fd;

        strcpy(key,(unsigned char*)s);

        fd=fopen("dev_query","w");

        encrypt_string(key,dev_query,outstring1);
        fprintf(fd,"%s",outstring1);fflush(fd);
        fclose(fd);
        printf("Length of outstring1=%d\n",strlen(outstring1));
        printf("decrypted dev_query =[%s]\n",outstring1);
}       

int encrypt_string(unsigned char *key,unsigned char *instring, char *outstring)
{
        unsigned char outbuf[1024] = {0};  /*  For string termination  */
        int outlen,tmplen;
        unsigned char iv[] = {1,2,3,4,5,6,7,8};
        EVP_CIPHER_CTX ctx;

        EVP_CIPHER_CTX_init(&ctx);
        EVP_EncryptInit(&ctx, EVP_bf_cbc(), key, iv);

        if(!EVP_EncryptUpdate(&ctx, outbuf, &outlen, instring, strlen(instring)))
                 {
                 return 0;
                 }

        if(!EVP_EncryptFinal(&ctx, outbuf + outlen, &tmplen))
                 {
                 return 0;
                 }

        outlen += tmplen;
        printf("outlen=%d\n",outlen);
        EVP_CIPHER_CTX_cleanup(&ctx);
        strcpy(outstring,outbuf);
        return 1;
}


/* ---------------------------------------------------------------- 
 *       decrypt.c 
 *
 *      decrypt a encrypted string
 *
 */

#include <stdio.h>
#include <string.h>
#include <openssl/evp.h>

unsigned char dev_query[]={0xf5,0xb9,0x6f,0x14,0xd2,0x91,0x44,0x38,
                           0x06,0x2a,0x99,0xe0,0xff,0xde,0x87,0x05};

main(int argc, char *argv[])
{
        char decrypted[2048];
        unsigned char key[8];
        unsigned char instring[1024];
        char s[]="399";
        FILE *fd;

        fd=fopen("dev_query2","w");
        fprintf(fd,"%s",dev_query);
        fclose(fd);
        strcpy(key,(unsigned char*)s);
        strcpy(instring,dev_query);
        
        decrypt_string(key,instring,decrypted);
        printf("Development:\n");
        printf("\tseed=[%s]\n\tinput=[%s]\n\tdecrypted 
string=[%s]\n",s,dev_query,decrypted);
}

int decrypt_string(unsigned char *key,unsigned char *instring, char *outstring)
{
        unsigned char buf[1024] = {0};  /*  For string termination  */
        int outlen,tmplen;
        unsigned char iv[] = {1,2,3,4,5,6,7,8};
        EVP_CIPHER_CTX ctx;

        EVP_CIPHER_CTX_init(&ctx);
        EVP_DecryptInit(&ctx, EVP_bf_cbc(), key, iv);

        if(!EVP_DecryptUpdate(&ctx, buf, &outlen, instring, strlen(instring)))
                 {
                 return 0;
                 }

printf("ctx->cipher->block_size=%d\n",ctx.cipher->block_size);
printf("ctx->buf_len=%d\n",ctx.buf_len);
        if(!EVP_DecryptFinal(&ctx, buf + outlen, &tmplen))
                 {
                 return 0;
                 }

        outlen += tmplen;
        EVP_CIPHER_CTX_cleanup(&ctx);
/*      printf("decrypt value =[%s]  [%d]  [%d]\n\n", buf, key, outlen); */
        strcpy(outstring,buf);
        return 1;
}
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