Handycipher is a low-tech stream cipher, simple enough to permit pen-and-paper encrypting and decrypting of messages, while providing a significantly high level of security. Handycipher was first published in 2014 and further improved in 2015 and 2016. Part 10 of the Handycipher series presents the same challenge as Part 9 but with a different key choice. It is a ciphertext-only challenge.