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Explore Challenges

179 challenges found.

by newton, published on 11/27/2023

Ready for the Elliptic Boogaloo? In this challenge, we dance on elliptic curves and try to forge digital signatures.

by Eric Bond Hutton, published on 10/16/2023

An English plaintext of length 4272 was encrypted with the Hutton cipher, a pen-and-paper cipher from 2018. The length of the two passwords is also known. Can you successfully perform a ciphertext-only attack?

by Eric Bond Hutton, published on 9/6/2023

Unlock the secrets of the Hutton cipher, a pen-and-paper cipher from 2018. Can you crack the ciphertext?

by Eric Bond Hutton, published on 7/21/2023

Unlock the secrets of the Hutton cipher, a pen-and-paper cipher from 2018. Can you crack the ciphertext?

by Eric Bond Hutton, published on 6/5/2023

Unlock the secrets of the Hutton cipher, a pen-and-paper cipher that has baffled cryptographers since 2018. Can you reconstruct the keywords used?

by Eric Bond Hutton, published on 5/2/2023

Unlock the secrets of the Hutton cipher, a pen-and-paper cipher that has baffled cryptographers since 2018. Can you crack the ciphertext?

by Nils Kopal, published on 3/27/2023

The Josse cipher is a polyalphabetic cipher from the time of the Franco-Prussian War. Its description was lost. It was only rediscovered and published in 2020. In these challenges you are to decipher several, increasingly shorter ciphertexts.

by Nils Kopal, published on 2/25/2023

The Josse cipher is a polyalphabetic cipher from the time of the Franco-Prussian War. Its description was lost. It was only rediscovered and published in 2020. In these challenges you are to decipher several, increasingly shorter ciphertexts.

by Nils Kopal, published on 2/10/2023

The Josse cipher is a polyalphabetic cipher from the time of the Franco-Prussian War. Its description was lost. It was only rediscovered and published in 2020. In these challenges you are to decipher several, increasingly shorter ciphertexts.

by Nils Kopal, published on 10/28/2022

The Syllabary cipher seems to be just another substitution cipher. This time, the table got mixed up. Is a solution even possible? Find it out!

by Nils Kopal, published on 10/28/2022

The Syllabary cipher seems to be just another substitution cipher, but is it? Find out and solve its mystery! All keys went missing...

by Nils Kopal, published on 10/28/2022

The Syllabary cipher seems to be just another substitution cipher, but is it? Find out and solve its mystery! But this time, the table is weird...

by Nils Kopal, published on 10/28/2022

The Syllabary cipher seems to be just another substitution cipher, but is it? Find out and solve its mystery! A key got missing...

by Peter Uelkes, published on 10/14/2022

The legendary Merkle-Hellman Knapsack cryptosystem can also be used for public-key encryption. Is the cryptosystem secure or can you crack the ciphertext?

by Peter Uelkes, published on 9/4/2022

The historical Hill cipher uses matrix-vector multiplications to encrypt blocks of letters. Can you find the inverse matrix and recover the plaintext?

by Peter Uelkes, published on 5/14/2022

A more difficult and even more interesting sequel to the "Alberti Challenge - Part 1". Will you manage to crack this puzzle this time as well?

by Encrypted Puzzle, published on 1/24/2022

This cipher is a new take on the well-known Vigenère cipher. It has been designed to fix its "brother's" weaknesses. Can you find another weakness?

by Nils Kopal, published on 10/6/2021

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the last challenge in a series of 13 level-2 challenges with the SZ42. In this "key breaking" challenge you are provided with one ciphertext and parts of the corresponding plaintext. Can you find the MU wheel patterns and decrypt the ciphertext?

by Nils Kopal, published on 10/6/2021

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the twelfth challenge in a series of 13 level-2 challenges with the SZ42. In this "key breaking" challenge you are provided with one ciphertext and parts of the corresponding plaintext. Can you find the PSI wheel patterns and decrypt the ciphertext?

by Nils Kopal, published on 7/31/2021

The SIGABA CSP-2900 was a highly secure encryption machine used by the US for strategic communication in WWII. In this series of challenges, you are provided with a ciphertext and a partially-known plaintext, here with the length of 270 and 120 characters.

by Nils Kopal, published on 7/31/2021

The SIGABA CSP-2900 was a highly secure encryption machine used by the US for strategic communication in WWII. In this series of challenges, you are provided with a ciphertext and a partially-known plaintext, here with the length of 320 and 120 characters.

by Nils Kopal, published on 6/1/2021

The SIGABA CSP-889 was a highly secure encryption machine used by the US for strategic communication in WWII. In this series of challenges, you are provided with a ciphertext and a partially-known plaintext, here with the length of 270 and 120 characters.

by Nils Kopal, published on 6/1/2021

The SIGABA CSP-889 was a highly secure encryption machine used by the US for strategic communication in WWII. In this series of challenges, you are provided with a ciphertext and a partially-known plaintext, here with the length of 320 and 120 characters. Update June 2021: We replaced the used key (and this changed the ciphertext) since a part of the previous used key was leaked in the newest SIGABA template of CrypTool 2.

by madness, published on 5/21/2021

The Wheatstone Cryptograph is a simple device that resembles a clock with two hands. For each hand there is a ring of symbols. In this challenge the key is a random permutation of the english alphabet. Are you able to decrypt the given ciphertext?

by Nils Kopal, published on 1/30/2021

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the eleventh challenge in a series of 13 level-2 challenges with the SZ42. In this "key breaking" challenge you are provided with one ciphertext and the corresponding plaintext. Can you find the wheel patterns?

by Nils Kopal, published on 1/30/2021

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the tenth challenge in a series of 13 level-2 challenges with the SZ42. In this "key breaking" challenge you are provided with one ciphertext and the corresponding plaintext. Can you find the wheel patterns? Update January 2021: The starting positions for the CHI wheels were added.

by Nils Kopal, published on 12/19/2020

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the ninth challenge in a series of 13 level-2 challenges with the SZ42. In this "setting" challenge you are provided with only one ciphertext; the patterns for all the wheels are known as well as the starting positions for the CHI wheels. Can you find the starting positions for both the MU and PSI wheels and decrypt the ciphertext?

by Nils Kopal, published on 10/31/2020

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the eighth challenge in a series of 13 level-2 challenges with the SZ42. In this "setting" challenge you are provided with only one ciphertext; the patterns for all the wheels are known as well as the starting positions for the CHI and PSI wheels. Can you find the starting positions for the MU wheels and decrypt the ciphertext?

by Nils Kopal, published on 10/27/2020

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the seventh challenge in a series of 13 level-2 challenges with the SZ42. In this "setting" challenge you are provided with only one ciphertext; the patterns for all the wheels are known as well as the starting positions for the CHI and MU wheels. Can you find the starting positions for the PSI wheels and decrypt the ciphertext?

by Nils Kopal, published on 10/2/2020

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the sixth challenge in a series of 13 level-2 challenges with the SZ42. In this "setting" challenge you are provided with only one ciphertext and the patterns for all five CHI wheels are known. Can you find the starting positions for the five CHI wheels?

by Nils Kopal, published on 9/3/2020

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the fifth challenge in a series of 13 level-2 challenges with the SZ42. In this "setting" challenge you are provided with only one ciphertext and the patterns for CHI1 and CHI2 wheels are known. Can you find the starting positions for CHI1 and CHI2?

by Nils Kopal, published on 8/29/2020

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the fourth challenge in a series of 13 level-2 challenges with the SZ42. In this "setting" challenge you are provided with only one ciphertext and the patterns for CHI1 and CHI2 wheels are known. Can you find the starting positions for CHI1 and CHI2?

by Nils Kopal, published on 8/15/2020

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the third challenge in a series of 13 level-2 challenges with the SZ42. Here, you are provided with 2 in-depth ciphertexts and a limitation is used. Can you recover the plaintexts?

by Nils Kopal, published on 8/5/2020

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the second challenge in a series of 13 level-2 challenges with the SZ42. Here, you are provided with 4 in-depth ciphertexts and a limitation is used. Can you recover the plaintexts?

by Nils Kopal, published on 7/22/2020

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the first challenge in a series of 13 Level-2 challenges with the SZ42. Here, you are provided with 8 in-depth ciphertexts. Can you recover the plaintexts?

by Miroslav Dimitrov, Bernhard Esslinger, published on 7/16/2020

This is part 3 of the challenge series about lattice-based cryptography schemes. This challenge introduces an encryption scheme which uses systems of linear equations. Can you decrypt a message without knowing the key?

by madness, published on 4/6/2020

This part of the challenge series introduces polyhomophonic substitution. In a polyhomophonic substitution cipher, each ciphertext symbol can represent one of several plaintext symbols, and each plaintext letter can be encrypted as one of several ciphertext letters. The key is a mapping from the set of plaintext symbols to the set of ciphertext symbols.

by madness, published on 3/28/2020

This part of the challenge series is a warm-up with polyphonic substitution. In a polyphonic substitution cipher, more than one plaintext letter are encrypted to the same ciphertext symbol. The key is a mapping from the set of plaintext symbols to the set of ciphertext symbols.

by George Lasry, published on 3/5/2020

The SIGABA was a highly secure encryption machine used by the US for strategic communications in WWII. As in part 1 of this series of challenges, you are provided with a partial known-plaintext, and some information about the key settings. However, in this part you get less information about the key.

by George Lasry, published on 2/29/2020

The SIGABA was a highly secure encryption machine used by the US for strategic communications in WWII. It is believed that the German codebreakers were unable to make any inroads against SIGABA. In this part of the series of challenges, you are provided with a partial known-plaintext, and some information about the key settings.