http://ocw.cs.pub.ro/courses/ 2026-06-10T11:59:53+03:00 http://ocw.cs.pub.ro/courses/ http://ocw.cs.pub.ro/courses/lib/tpl/arctic/images/favicon.ico text/html 2020-10-18T15:55:22+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/01?rev=1603025722&do=diff Laboratorul 01 - Introduction Python3 Crash Course Check-out this tutorial: here. Encoding vs Encryption Encoding * Is used to transform data from one format to another. * Typically used in data transfer between different systems. * The information is NOT kept secret!!! * To decode the encoded data you only need to know the algorithm that was used. text/html 2020-10-19T14:38:42+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/02?rev=1603107522&do=diff Laboratorul 02 - Shift and Vigenère Ciphers Please download the lab skeleton from here: The archive contains the following: * format_funcs.py: the format functions from the previous lab; * caesar.py: the implementation of the Caesar encryption and decryption from the previous lab; * msg_ex1.txt: the text which needs to be decrypted for exercise 1; * msg_ex2.txt: the text which needs to be decrypted for exercise 2; * msg_ex3.txt: the text which needs to be decrypted for exercise 3; … text/html 2020-10-26T00:03:54+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/03?rev=1603663434&do=diff Laboratorul 03 - PRGs import base64 # CONVERSION FUNCTIONS def _chunks(string, chunk_size): for i in range(0, len(string), chunk_size): yield string[i:i+chunk_size] def _hex(x): return format(x, '02x') def hex_2_bin(data): return ''.join(f'{int(x, 16):08b}' for x in _chunks(data, 2)) def str_2_bin(data): return ''.join(f'{ord(c):08b}' for c in data) def bin_2_hex(data): return ''.join(f'{int(b, 2):02x}' for b in _chunks(data, 8)) def str_2_hex(data): retu… text/html 2020-11-02T01:08:54+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/04?rev=1604272134&do=diff Laboratorul 04 - PRFs, PRPs, SPNs import base64 # CONVERSION FUNCTIONS def _chunks(string, chunk_size): for i in range(0, len(string), chunk_size): yield string[i:i+chunk_size] # THIS ONE IS NEW def byte_2_bin(bval): """ Transform a byte (8-bit) value into a bitstring """ return bin(bval)[2:].zfill(8) def _hex(x): return format(x, '02x') def hex_2_bin(data): return ''.join(f'{int(x, 16):08b}' for x in _chunks(data, 2)) def str_2_bin(data): return … text/html 2020-11-04T14:00:41+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/05?rev=1604491241&do=diff Laboratorul 05 - DES In this lab we'll do some exercises with DES and some of its variants, as we discussed in the last lecture here. import base64 # CONVERSION FUNCTIONS def _chunks(string, chunk_size): for i in range(0, len(string), chunk_size): yield string[i:i+chunk_size] def byte_2_bin(bval): return bin(bval)[2:].zfill(8) def _hex(x): return format(x, '02x') def hex_2_bin(data): return ''.join(f'{int(x, 16):08b}' for x in _chunks(data, 2)) def str_2_bin(data)… text/html 2020-11-03T10:04:46+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/06?rev=1604390686&do=diff Laboratorul 06 - AES Byte at a Time ECB Decryption AES ECB The simplest of the encryption modes is the Electronic Codebook (ECB) mode (named after conventional physical codebooks). The message is divided into blocks, and each block is encrypted separately. text/html 2018-11-05T14:25:53+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/07?rev=1541420753&do=diff Laboratorul 07 - Correlation Power Analysis In this lab we'll implement a side-channel attack known as Correlation Power Analysis. The principle is quite simple: * Choose your target (generally the S-box output of some block cipher - in our case AES) * Obtain a large number (thousands) of leakage samples for that target, when processing different plaintexts * Choose a suitable leakage model (usually the hamming weight of the target value) * For each possible key candidate (e.g. all va… text/html 2020-11-05T17:01:26+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/08?rev=1604588486&do=diff Laboratorul 08 - MACs In this lab we'll do some exercises with Message Authentication Codes. Exercise 1 - Existential Unforgeability In this exercise we will attack an insecure MAC algorithm by showing that an adversary can forge a (message, tag) pair without first querying a oracle with the message. text/html 2020-11-05T17:54:27+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/09?rev=1604591667&do=diff Laboratorul 09 - OpenSSL MACs, Hashes and AEAD Exercise 1 In this exercise we'll use the command line to compute an HMAC, with SHA-1 as the hashing algorithm. Recall from the lecture that for HMAC to be secure, we need to sample a random key . We can generate random bytes using openssl rand. To compute HMACs, check the documentation for openssl dgst. text/html 2020-11-05T17:52:43+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/10?rev=1604591563&do=diff Laboratorul 10 OLD - OpenSSL AEAD Before you start solving the exercises below, download the [lab archive from here]. Exercise 1 The archive contains the source code for Exercise 2, but sadly it is encrypted. Luckily, we forgot to remove the password file from the archive. text/html 2020-11-05T17:53:28+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/11?rev=1604591608&do=diff Laboratorul 10 - Public key encryption In this lab we'll do some cool exercises using public key encryption methods for key exchange and data encryption. Exercise 1: Diffie-Hellman key exchange (4p) As we discussed in class, Diffie and Hellman proposed the first public key exchange mechanism such that two parties, that did not share any previous secret could establish a common secret. This allows the parties to have a shared key that only they know (except if there is an active man in the mid… text/html 2016-09-28T15:02:05+03:00 http://ocw.cs.pub.ro/courses/ic/laboratoare/12?rev=1475064125&do=diff Laboratorul 12.