This cipher text was encrypted using the Playfair cipher.
Since similar keys result in similar ciphertexts for a given plaintext, the playfair cipher is susceptible to optimization algorithms. Start with a random key or several random keys, and optimize until the decrypted ciphertext appears to be English. Some useful algorithms are Simulated Annealing and Genetic Algorithms. The plaintext describes how to submit the solution.
Test VectorUsing the pass phrase
TESTINGresults in the key
TESIN GABCD FHKLM OPQRU VWXYZThe message
hello worldis preprocessed to
HELXOWORLD. Notice that the second 'L' was converted to an 'X'. This plain text is encrypted to