1-4 1st woman and 2nd man cross giving right hands while 3rd woman casts up as 2nd woman steps down. Then 2nd man and 3rd woman pass each other right shoulder on the sides as 1st woman and 3rd man pass left shoulder.
5-8 3rd man, 2nd man, 1st woman and 2nd woman (in the bottom two places) dance left hands across one and a quarter times ending on the sides. 1st woman and 3rd woman are in exchanged places, all others are back in original places.
9-12 1st woman and 2nd man cross giving left hands while 3rd woman casts off as 2nd woman steps up. Then 1st couple pass each other right shoulder on the sides as 3rd woman and 2nd man pass left shoulder.
13-16 1st and 2nd couples circle four hands round one and a quarter to the left so that all are now back in original places.
17-20 All dance a modified set and link for three couples. All set on the sides, those with left hand free coming into the centre. Then 2nd couple and those with right hand free (1st woman and 3rd man) cast clockwise to the ends as usual. Meanwhile 1st man and 3rd woman turn once round with the left hand to end in the centre facing up/down to the ends.
21-24 The three men at the top and three women at the bottom dance right hands across. 1st man and 3rd woman end on the diagonal facing their 2nd corner positions which are occupied by 2nd man and 2nd woman respectively. 3rd man and 1st woman end in 1st and 3rd places on their own sides.
25-28 2nd man, 1st man, 3rd woman and 2nd woman dance half a right shoulder diagonal reel of four. 1st man and 3rd woman end passing right shoulders to own sides. The men are now in the order 3,1,2 and the women in the order 2,3,1.
29-32 All turn new partners once round with both hands.
(Dance Crib compiled by the deviser, Murrough Landon, CC BY-SA March 2019)
The Enigma Machine had three coding wheels which were used to scramble messages into a ciphered form or to decipher encoded messages. These are represented here by hands across, circles and turning with both hands.
Cryptographic literature often uses a few stock characters to illustrate problems. Alice and Bob are the main actors who hope to exchange secret messages without them being intercepted or decrypted by Eve, the eavesdropper. Here 1st woman and 2nd man are Alice and Bob while 3rd woman is Eve.
Bars 1-8 and 9-16 represent encryption and decryption with Alice and Bob exchanging places as Eve tries to get close to Bob. The final progression is suitably scrambled with all changing partners. Alice and Bob end up together for the repeat.
(Dance Information compiled by the deviser, Murrough Landon, CC BY-SA March 2019)
Enigma has an electromechanical rotor mechanism that scrambles the 26 letters of the alphabet. In typical use, one person enters text on the Enigma's keyboard and another person writes down which of 26 lights above the keyboard lights up at each key press. If plain text is entered, the lit-up letters are the encoded ciphertext. Entering ciphertext transforms it back into readable plaintext. The rotor mechanism changes the electrical connections between the keys and the lights with each keypress. The security of the system depends on Enigma machine settings that were changed daily, based on secret key lists distributed in advance, and on other settings that change for each message. The receiving station has to know and use the exact settings employed by the transmitting station to successfully decrypt a message.
As used in practice, the Enigma encryption proved vulnerable to cryptanalytic attacks by Germany's adversaries, at first Polish and French intelligence and, later, a massive effort mounted by the United Kingdom at Bletchley Park. While Germany introduced a series of improvements to Enigma, and these hampered decryption efforts to varying degrees, they did not ultimately prevent Britain and its allies from exploiting Enigma-encoded messages as a major source of intelligence during the war. Many commentators say this flow of communications intelligence shortened the war significantly and may even have altered its outcome.