In 1916, the USA bought the West Indian islands from Denmark. An encrypted telegram about this purchase, sent by the Danish ambassador, is available on a website.

In 1921 an encrypted telegram was sent from the Portuguese embassy in Berlin to Lisbon. The plaintext is known, but the encryption method used isn’t. Can a reader help?

In 1911, the British consul in Lüderitz, German South West Africa, sent an encrypted telegram to the foreign ministry in London. Can a reader break this encryption?

Three weeks ago I blogged about an encrypted telegram that was sent from New York to Tel Aviv in 1948. This cryptogram has now been solved.

In 1948 an encrypted telegram was sent  from New York to Tel Aviv, Israel. Can a reader break this encryption?

In one of his lectures, master codebreaker William Friedman once mentioned two encrypted telegrams. He knew the  solutions, but he didn’t reveal them. Can a reader break these encrypted messages?