ebCTF 2013 | cry100 « Classic » [Write Up]

« We found some crypto ciphers on our attic. Can you decipher all text and put together the flag? » In this first crypto challenge, we were given six classic ciphertexts to break. Each plaintext gave a part of the final flag ebCTF{md5}. I. Vigenere The first ciphertext was a simple vigenere : W yzrqc az […]

ebCTF 2013 | Cry200 « One to many » [Write Up]

« We identified some unground operatives that are using RSA to exchange messages with each other. We managed to incercept some, can you decrypt them? » In this crypto challenge, we were given 4096 text files containing n, the modulus, and encrypted_msg, the… encrypted message in RSA, for example: The modulus in each file were […]