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isc:labs:02 [2023/10/17 19:18] david.gherghita |
isc:labs:02 [2025/10/13 14:09] (current) david.gherghita [6. [10p] Feedback] |
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| ===== Exercises ===== | ===== Exercises ===== | ||
| - | === 0. [5p] AES ECB (Warmup) === | + | === 01. [5p] AES ECB (Warmup) === |
| It is recommended NOT to encrypt more than one block with AES in ECB mode, but in order to understand why, an image with the following header was encrypted. The encrypted photo cand be found {{isc:labs:isc-lab02-encrypted.zip|here (.zip)}}. Is it possible to figure out what the initial image was? | It is recommended NOT to encrypt more than one block with AES in ECB mode, but in order to understand why, an image with the following header was encrypted. The encrypted photo cand be found {{isc:labs:isc-lab02-encrypted.zip|here (.zip)}}. Is it possible to figure out what the initial image was? | ||
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| </solution> | </solution> | ||
| - | === 1. [20p] AES === | + | === 02. [20p] AES === |
| {{:isc:labs:isc-lab02-secret.zip|This file (compressed as .zip)}} was encrypted using the following code. Can you decrypt it? | {{:isc:labs:isc-lab02-secret.zip|This file (compressed as .zip)}} was encrypted using the following code. Can you decrypt it? | ||
| - | <code> | + | <code python> |
| from Crypto.Cipher import AES | from Crypto.Cipher import AES | ||
| from Crypto import Random | from Crypto import Random | ||
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| <solution -hidden> | <solution -hidden> | ||
| - | <code> | + | <code python> |
| from Crypto.Cipher import AES | from Crypto.Cipher import AES | ||
| Line 216: | Line 216: | ||
| </solution> | </solution> | ||
| - | === 2. [20p] RSA - Known factorisation === | + | === 03. [20p] RSA - Known factorisation === |
| In order to decrypt the ciphertext, you need to factorize n into p and q, compute phi and find d. | In order to decrypt the ciphertext, you need to factorize n into p and q, compute phi and find d. | ||
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| </code> | </code> | ||
| * **Note**: the result is a decimal number, you need to convert it to an ASCII text using the snippet below: | * **Note**: the result is a decimal number, you need to convert it to an ASCII text using the snippet below: | ||
| - | <code> | + | <code python> |
| print(hex(message)[2:].decode("hex")) # python 2 | print(hex(message)[2:].decode("hex")) # python 2 | ||
| print(bytearray.fromhex(hex(message)[2:])) # python 3 | print(bytearray.fromhex(hex(message)[2:])) # python 3 | ||
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| <solution -hidden> | <solution -hidden> | ||
| - | <code> | + | <code python> |
| import gmpy2 | import gmpy2 | ||
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| </solution> | </solution> | ||
| - | ==== 03 [15p] Is this even OTP? ==== | + | ==== 04. [15p] Is this even OTP? ==== |
| * Someone applied [[https://en.wikipedia.org/wiki/One-time_pad|one time pad]] on {{:isc:labs:isc-lab02-otp.txt|this text}}. | * Someone applied [[https://en.wikipedia.org/wiki/One-time_pad|one time pad]] on {{:isc:labs:isc-lab02-otp.txt|this text}}. | ||
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| <solution -hidden> | <solution -hidden> | ||
| - | <code> | + | <code python> |
| + | |||
| + | # Key = 1e: i_guess_it_kinda_is_otp | ||
| + | |||
| + | from itertools import cycle | ||
| + | |||
| + | c = 'wAyk{mmAwjAuwpzAwmAqjn' | ||
| - | Key = 1e: i_guess_it_kinda_is_otp | + | for i in range(0,256): |
| + | print("".join([chr(x[0] ^ ord(x[1])) for x in zip(cycle([i]), c)])) | ||
| </code> | </code> | ||
| </solution> | </solution> | ||
| - | ==== 04 [20p] Many Time Pad ==== | + | ==== 05. [20p] Many Time Pad ==== |
| * This time, {{:isc:labs:isc-lab02-many_time_pad.zip|he did use a proper key}}. Unfortunately for him, he used it for multiple encryptions. | * This time, {{:isc:labs:isc-lab02-many_time_pad.zip|he did use a proper key}}. Unfortunately for him, he used it for multiple encryptions. | ||
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| </solution> | </solution> | ||
| - | ==== 05 [20p] We want Jokes instead of Nukes ==== | + | ==== 06. [20p] We want Jokes instead of Nukes ==== |
| * {{:isc:labs:isc-lab02-oracle.zip|Donald has gone completely crazy}}. To prevent world chaos, you kidnapped him. Right before the kidnapping he tried to send one encrypted message to his wife Melania. Luckily you intercepted the message. Donald admits that he used AES256-CBC encryption - a block cipher operating with a block length of 16 bytes. | * {{:isc:labs:isc-lab02-oracle.zip|Donald has gone completely crazy}}. To prevent world chaos, you kidnapped him. Right before the kidnapping he tried to send one encrypted message to his wife Melania. Luckily you intercepted the message. Donald admits that he used AES256-CBC encryption - a block cipher operating with a block length of 16 bytes. | ||
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| <solution -hidden> | <solution -hidden> | ||
| - | <code> | + | <code python> |
| original_iv = bytes.fromhex('7ec00bc6fd663984c1b6c6fd95ceeef1') | original_iv = bytes.fromhex('7ec00bc6fd663984c1b6c6fd95ceeef1') | ||
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| </solution> | </solution> | ||
| - | + | ==== 07. Feedback ==== | |
| - | ==== 6. [10p] Feedback ==== | + | |
| Please take a minute to fill in the [[https://docs.google.com/forms/d/e/1FAIpQLSeMrKoWY6UKe1N_BASUARA-HixTuvSfrEnx_FKstT-RW464NQ/viewform |feedback form]] for this lab. | Please take a minute to fill in the [[https://docs.google.com/forms/d/e/1FAIpQLSeMrKoWY6UKe1N_BASUARA-HixTuvSfrEnx_FKstT-RW464NQ/viewform |feedback form]] for this lab. | ||
