## Captain Walter Fried's Fish Notes March 1944 to January 1945## Page 21 |
Tony Sale's Codes and Ciphers |

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- TOP SECRET CX/MSS Page 6

impulses (considered cyclically so that 1 and 5 are adjacent). A dot in

the permutation key means that the permuting factor is operative, a cross

that it is inoperative. The first position of the permutation key represents an

interchange between impulses 1 and 5, the second between 5 and 4,

the third between 4 and 3, the fourth between 3 and 2 and the fifth between

2 and 1. The order in which the permutations take place is significant

and in enciphering they proceed in the left to right order of the key, i.e.

.xxx. would cause 12345 to become 52341 after the first permutation and

25341 after the second. In deciphering the order is reversed and this is

the reason for using the symbol pi^(-1).

- 17. The most interesting feature of the machine is the motor action.

of the machine getting into a rut both dots and crosses act as motor

impulses. Wheel A, for example, might~be driven by dots in B and crosses

in C. Either a dot in B or a cross in C will cause it to move and it will

fail to advance only if there is a cross in B and a dot in C. The motor

action is controlled by a portion of the pattern different than the portion

operative for encipherment, but there is a fixed relation. The operative

motor element is behind the enciphering element an interval which is the

nearest integer under 2/3 of the wheel period (or ahead by an interval which

is the nearest integer above 1/3 of the period). In the case of the 69

wheel the figure is exactly 46 (or 23). if, for example, the 47 wheel is

at position 8 for enciphering, its 24th position will control its effect

as a motor wheel.

- 18. The motor relations, which seem to be invariant, are as follows:

Wheel Driven by

47 65 crosses, 67 dots

53 47 cross6s, 73 dots

59 47 dots, 53 crosses

61 53 dots, 59 dots

64 59 crosses, 61 crosses

65 61 dots, 64 crosses

67 64 dots, 65 dots

69 " "

71 " "

73 " "

motor is to insure a minimum key length of the product of their cycles. The

machine must contain a switch with which the motor action can be thrown on

or off because instances have been observed where the motor is not used. In

such cases each wheel steps forward one position for each letter enciphered.