# All posts by Alkanor

# [NDH 2016] [Stegano 150 – hamming fury] Write Up

## Description

not saved

# Hamming fury

We were a bit disappointed when we solved it 15 minutes after the end of the CTF (modulo RER transport), but however happy to find the flag.

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# [Sharif University CTF 2016] [Crypto 100 – Universal re-encryption] Write Up

## Description

Universal Re-Encryption

Let p be a prime, and g be an element of ℤ/pℤ of prime order q.

Let x ∈ ℤ/qℤ be the private key, and h = g^x (mod p) be the public key.To encrypt a message m ∈ ℤ/pℤ, pick two random values r, s ∈ ℤ/qℤ, and compute the ciphertext as follows:

(a, b, c, d) = (g^r, h^r, g^s, mh^s).Download a valid ciphertext σ = (a, b, c, d) below, and compute another valid ciphertext σ′ = (a′, b′, c′, d′) such that:

σ and σ′ decrypt to the same message;

a ≠ a′ and b ≠ b′ and c ≠ c′ and d ≠ d′.

Continue reading [Sharif University CTF 2016] [Crypto 100 – Universal re-encryption] Write Up

# [HackIM 2016] [Misc 400 – Lol] Write Up

## Description

52.91.163.151:30303

===Win this simple text decoder and take your flag !===

# [HackIM 2016] [Crypto 500 – Crypto question 1] Write Up

## Description

Crypto Question 1 500 pts

You are in this GAME. A critical mission, and you are surrounded by the beauties, ready to shed their slik gowns on your beck. On onside your feelings are pulling you apart and another side you are called by the duty. The biggiest question is seX OR success? The signals of subconcious mind are not clear, cryptic. You also have the message of heart which is clear and cryptic. You just need to use three of them and find whats the clear message of your Mind… What you must do?

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