Klaus Schmeh

Klaus Schmeh ist Experte für historische Verschlüsselungstechnik. Seine Bücher "Nicht zu knacken" (über die zehn größten ungelösten Verschlüsselungsrätsel) und "Codeknacker gegen Codemacher" (über die Geschichte der Verschlüsselungstechnik) sind Standardwerke. In "Klausis Krypto Kolumne" schreibt er über sein Lieblingsthema.

Blog reader Christof Rieber has sent me a potential solution of a major crypto mystery: the encrypted passages of Lady Gewndolen’s diary. Is Christof’s deciphering attempt correct?

In 1914, a man sent an encrypted postcard from Kiel to Hannoversch Münden. Contrary to all other encrypted postcards I know, this one was written with a typewriter.

At the hacker conference 44CON 2019, wich took place in September in London, I gave a talk about Cold War cryptography. Here’s a professionally produced video of it.

Blog reader Norbert Biermann has recently solved a bigram substitution ciphertext consisting of 1346 letters – the shortest one ever broken. Here’s a 1000-letter ciphertext of the same kind.

During a stay in the Austrian capital of Vienna, I tried to take a look at the encrypted inscription on the cenotaph of Duke Rudolf IV. I was only partially successful.

In 1920, IRA member Patrick James McGuire received an encrypted Easter postcard. Does it contain a love message? Or is the content related to the Irish War of Independence?

In 1873, an unknown person published two encrypted advertisements in the Daily Telegraph. Can a reader break these cryptograms?

At the NSA Symposium on Cryptologic History, I will give a presentation about brute-force attacks. There’s one thing I still haven’t figured out: when was the first brute-force described or carried out?

In 1916, a man living in Aschersleben, Germany, received an encrypted postcard. Can a reader decipher it?

Sometimes, deciphering a cryptogram is easier than reading the deciphered message. Here are two plaintexts I have difficulties to understand.