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 Course: Seminar Topic: Seminar Description: Gunjan and I gave a seminar on Enigma Cipher. We started by giving an introduction to Substitution Cipher
Substitution Cipher : It involves substituting one letter for another according to some rule. This is the principle underlying the Enigma. An example of substitution is :
ABCDEFGHIJKLMNOPQRSTUVWXYZ IPHBOSFCQZJNTWGLMYRXDKEUVA
Enigma Machine :-
The Enigma Machine was invented in 1918 by Arthur Scherbius in Berlin. It enciphers a message by performing a number of substitutions one after the other. Scherbius's idea was to achieve these substitutions by electrical connections.
A_B_C_D_E_F_G_H_I_J_K_L_M_N_O_P_Q_R_S_T_U_V_W_X_Y_Z
I_P_H_B_O_S_F_C_Q_Z_J_N_T_W_G_L_M_Y_R_X_D_K_E_U_V_A
K_A_L_B_M_C_N_D_O_E_P_F_Q_G_S_H_R_I_T_J_U_W_Z_Y_X_V

# The voltage appearing at the M terminal carries on to the R terminal on the bottom row. Thus the wirings have achieved a 'substitution' first from Q to M and then from M to R.

** The weaknesses in the machine:
(which were much exploited and taken advantage of , by the Polish people to break into Enigma)
• 1. No letter can ever encipher to itself.
• 2. They required the operator to key in the message key letters twice in succession and transmit the six letters that resulted.

In order to convey the Message Key (the complete and exact configuration of the machine in its starting position) to the intended recipient of the message, the Germans followed Scherbius’s original suggestion and decided to specify exactly everything except the rotor start position for each 24-hour period. This was achieved by pre-printing setting sheets- a months settings on one sheet, which was distributed by courier.

The breaking of the Enigma by the Polish Mathematicians
As German military power increased during the 1920’s, the Poles felt threatened. The modern use of radio allowed them to intercept enemy radio transmission without revealing their intelligence activities. A young team of Polish Mathematician tried their mathematical approach to break into Enigma. It included:-
• Jerzy Rozycki
• Henryk Zygalski
• Marian Rejewski