当我们在系统里“删除”了一个文件时，并不意味着这个文件就一定从磁盘上清除了，很多优秀的文件恢复软件都可以恢复被删除的文件，这在一定程度上就带来了隐私泄露的隐患。好在现在很多软件，比如360、电脑管家等等软件都集成了文件粉碎的实用功能。今天介绍一种以前被用于美国国防部的机密文件销毁算法，并附上实现的代码（C）。
算法介绍：
美国国防部DOD5220.22M文件销毁标准包括以下三步:
将文件先用0×00覆盖，再用0×01覆盖，如此重复三次；
将文件用一个随机值覆盖；
将文件名改为一个单字符文件名，最后删除之。
算法可靠性验证：
此算法虽然已经不再被美国国防部采用，但也足够应付一般的环境，主流文件恢复软件恢复的可能性还有待验证。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 | /* * File Destroyer 文件安全销毁 * * Copyright (C) 2015 Chaobs * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. * * E-mail: chaobs@outlook.com * Blog: www.cnblogs.com/chaobs * * 用法: file-destroyer [filename1] <filename2>... * * 算法介绍： * 基于美国国防部DOD5220.22M标准进行文件销毁，包括以下三步: * （1）将文件先用0x00覆盖，再用0x01覆盖，如此重复三次； * （2）将文件用一个随机值覆盖； * （3）将文件名改为一个单字符文件名，最后删除之。 * * 算法可靠性验证： * 此算法虽然已经不再被美国国防部采用，但也足够应付一般的环境，对于主流文件恢复软件恢复的可能性还有待验证。 * */#include <stdio.h>#include <stdlib.h>#include <time.h>voidnotice(inti, char*s); /* print short notice */voidwipe(FILE*f, charc); /* core func */longfile_size(FILE*f); /* get the size of a file */intrequire(intc, char*s[]);intmain(intargc, char*argv[]){ inti, j; charch; FILE*f; notice(1, argv[0]); if(argc < 2) { /* too few arguments */ notice(2, argv[0]); exit(0); } if(!require(argc, argv)) { fprintf(stderr, "Cancel Operating.\n"); exit(0); /* cancel */ } srand(time(NULL)); /* randomize */ for(i = 1; i < argc; ++i) { /* process each file */ if((f = fopen(argv[i], "r+b")) == NULL) {/* fail to open file */ fprintf(stderr, "Error when open %s:\n", argv[i]); exit(0); } for(j = 0; j < 3; ++j) { /* DOD5220.22M Step 1 */ wipe(f, 0x00); wipe(f, 0x01); } wipe(f, rand() % 256); /* Step 2 */ if(rename(argv[i], "C")) { /* Step 3*/ fprintf(stderr, "Error when rename %s\n", argv[i]); exit(0); /* XXX:文件名冲突的解决？可以考虑使用tmpnam()吗？*/ } remove("C"); /* XXX:如果是一个符号连接怎样保证删除的是真正的文件？ */ fclose(f); } printf("Done! Destroy %d files\n", argc - 1); return0;}/* implementation */voidnotice(inti, char*s){ if(i == 1) { printf("\nFile Destroyer Copyright (C) 2015 Chaobs\n"); printf("This program comes with ABSOLUTELY NO WARRANTY.\n"); printf("This is free software, and you are welcome to redistribute under certain conditions.\n\n"); } else{ fprintf(stderr, "Usage: %s [filename1] <filename2> ...\n", s); }}voidwipe(FILE*f, charc){ longi; longlen = file_size(f); /*获得文件长度*/ for(i = 0; i < len; ++i) fwrite(&c, 1, 1, f); /* overwrite */}longfile_size(FILE*f){ longlen; fseek(f, 0, SEEK_END); /* jump to the and of file */ len = ftell(f); fseek(f, 0, SEEK_SET); /* restore */ returnlen; /*感谢网友冰尘醉*/}intrequire(intc, char*s[]){ inti; charch; for(i = 1; i < c; ++i) { /* FIXME: the comfirm function can make mistakes and * it is not convenient even can't work in some cases. */ printf("Do you want to destroy %s ?(y/n) ", s[i]); ch = getchar(); getchar(); /* '\n' */ if(ch == 'n') return0; } return1;} |
滇公网安备 53230102000482号