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| - | ====== Lab 8 - Cryptography ====== | ||
| - | - [2p] There are several tools used for hiding files behind an image. Create a file “Lab08.txt” and add the following line: “Thanks GOD that this lab is NOT part of the exam.” Use jphide.exe and jpseek.exe to hide this info behind a JPG file. (http://images.google.com/ fileype:jpg) | ||
| - | - [+1p=3p] Archive the jphide.exe file into a .7z file using the 7zip utility already installed. Combine the image you’ve previously downloaded with this file using the copy.exe command in cmd. Make it a binary copy of those to files into a new .jpg file. What is the size of the new file? How can you reveal the archive created? | ||
| - | - [+1p=4p] Write in a notepad your name using the Caesar cipher. The key is equal to the number of letter in your name. (use both first and last names) | ||
| - | - [+2=6p] You have to use the following algorithm((Interesting fact: this algorithm is used for type 7 decryption in Cisco IOS.)) to decrypt the message “08324F5C”. <code c> | ||
| - | const char *xlat = "dsfd;kfoA,.iyewrkldJKDHSUBsgvca69834ncxv"; | ||
| - | |||
| - | char *unseven(const char *hash) | ||
| - | { | ||
| - | unsigned int key, i, hlen = strlen(hash) - 2; | ||
| - | char *plain = (char*)malloc(hlen / 2 + 1); | ||
| - | |||
| - | if (hlen < 2 || hlen & 1) return NULL; | ||
| - | |||
| - | key = (hash[0] - '0') * 10 + hash[1] - '0'; | ||
| - | if (key > 15 || !isdigit(hash[0]) || !isdigit(hash[1])) return NULL; | ||
| - | |||
| - | hash += 2; | ||
| - | for (i = 0; i < hlen; ++i) if (!isxdigit(hash[i])) return NULL; | ||
| - | |||
| - | for (i = 0; i < hlen; i += 2) { | ||
| - | plain[i / 2] = ((hex2int(hash[i]) << 4) | hex2int(hash[i + 1])) ^ xlat[key++]; | ||
| - | if (key == 40) key = 0; | ||
| - | } | ||
| - | plain[hlen / 2] = 0; | ||
| - | |||
| - | return plain; | ||
| - | } | ||
| - | </code> | ||
| - | - Hint: http://www.asciitable.com/ | ||
| - | - Hint: http://www.cprogramming.com/tutorial/bitwise_operators.html | ||
| - | - [+1=7p] Try to access the picture file from the USB. Now, import the certificate from the archive to your local computer. Try again. | ||
| - | - [+1=8p] Generate a certificate using the cipher.exe utility from Windows cmd. Encrypt one of you local directories (C:\Facultate\SCR). Now switch to another user (e.g.: PR) and try to access that directory. | ||
| - | * Hint: http://technet.microsoft.com/en-us/library/bb457065.aspx#EHAA | ||
| - | - [+1=9p] Create a certificate for the previously user (PR) and make sure that this user can also access the file, only two users can access the file. | ||
| - | - [+2=11p] Encryption contest. Create a symmetric encryption algorithm that uses substitution/transposition method applied directly on a block. Start! | ||
