An apparently unsolvable logic problem is wrapped in this cipher, but does that mean the cipher itself has no weakness? Meet Lady Liz and "relative encryption", which turns two characters into one.

Fialka was a rotor cipher machine used by the USSR during the Cold War. This third part comes without a punchcard. Can you still break the machine?

Fialka was a rotor cipher machine used by the USSR during the Cold War. This second part challenges your understanding of the machine. Despite longer keys being used, can you still break the machine?

Fialka was a rotor cipher machine used by the USSR during the Cold War. This challenge gives you the opportunity to understand the machine and test your skills at breaking it.

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?

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?

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?

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

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

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?

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

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

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

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

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.

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.

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.

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?

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!

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

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...

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

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

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

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?

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

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?

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

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?

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?

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?

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.

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.

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.

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.

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.

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.

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?

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?

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?