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Explore Challenges

368 challenges found.

by Jörg Drobick, published on 6/10/2024

During the Cold War, anyone could encrypt relatively securely with the PX-1000. To prevent this, the NSA added a backdoor in the successor model PX-1000cr. However, even the supposedly secure original version has weaknesses. Can you break the PX-1000?

by newton, published on 3/9/2024

Ready for the third Elliptic Boogaloo? In this challenge, we dance on elliptical curves and try to forge digital signatures. But some hints went missing. However, a nasty encryption algorithm prevents us from putting the necessary pieces of the puzzle together. Can you still manage to forge a signature?

by newton, published on 1/15/2024

Ready for the second Elliptic Boogaloo? In this challenge, we dance on elliptical curves and try to forge digital signatures. But some hints went missing. Can you still forge a signature?

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 M. Mertens, published on 10/31/2023

This challenge is a puzzle about a mysterious ciphertext, which is also protected by a clever disguise. Can you crack it?

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 12/30/2022

The Lorenz SZ42, codenamed Tunny, was a German teleprinter encryption device used during WW2. This is the fourteenth challenge in a series of 16 level-3 challenges with the SZ42. In this "Breaking" challenge you are only provided with one ciphertext. Can you find the MU-, CHI-, and PSI wheel patterns and decrypt the ciphertext?

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 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!

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 10/14/2022

The legendary Merkle-Hellman Knapsack cryptosystem is not suitable for hiking, but it is considered a pioneer of asymmetric cryptography. 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 Peter Uelkes, published on 3/26/2022

This challenge is about one of the oldest polyalphabetic ciphers. Can you crack this centuries-old puzzle?

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 200 and 100 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 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 200 and 100 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 madness, published on 4/21/2021

The Wheatstone Cryptograph is a simple device that resembles a clock with two hands. For each hand there is a ring of symbols. 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 Viktor Veselovsky, published on 12/26/2020

This series deals with a grid — a basic tool cryptographers use to separate sequences of data into columns and rows. In this challenge you are given three grids where the first grid gives you hints to reveal the plaintext of the second grid. Are you able to find the right route?

by Viktor Veselovsky, published on 12/19/2020

This series deals with a grid — a basic tool cryptographers use to separate sequences of data into columns and rows. In this challenge you are given four grids where the first grid gives you hints to reveal the plaintext of the second grid. Are you able to find the right route?

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?