When Yevgenia Ginzburg became a prisoner at Stalin’s Black Lake prison in the 1930s, she and her cellmate noticed a curious pattern. “On the days when our neighbor went to the washroom before us — this we could tell by the sound of the footsteps in the corridor — we always found the shelf sprinkled with tooth powder and the word ‘Greetings’ traced in it with something very fine like a pin, and as soon as we got back to our cell, a brief message was tapped on the wall. After that, he immediately stopped.”

After two or three days, she realized what it meant. “‘Greetings’! That’s what he’s tapping. He writes and taps the same word. Now we know how we can work out the signs for the different letters.” Ginzburg remembered a page from Vera Figner’s memoir in which she described an ancient prison code devised in the Czarist era — the alphabet was laid out in a square (this example is in English):

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

Each letter is represented by two sets of taps, one slow and the other fast. The slow taps indicate the row and the fast the column. So, here, three slow taps followed by two fast ones would indicate the letter L. They tapped out “Who are you?”, and “Through the grim stone wall we could sense the joy of the man on the other side. At last we had understood! His endless patience had been rewarded.”

Prisoner Alexander Dolgun deciphered the same code in Moscow’s Lefortovo Prison, memorizing it with the help of matches. Finally he understood that the man in the next cell had been asking him “Who are you?” over and over — and felt “a rush of pure love for a man who has been asking me for three months who I am.”

(From Judith A. Scheffler, Wall Tappings, 1986.)