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.

In July, I introduced a bigram substitution challenge consisting of 1346 letters. Norbert Biermann has now solved it. It’s the shortest ciphertext of this kind that has ever been broken.

Substituting letter pairs (also known as bigrams or digraphs) is an encryption method invented in the 16th century. Can you break a new challenge I have made?

Substituting letter pairs (bigrams) is an encryption method that was already known in the 16th century. Is it still secure today?