by Kahn, David
The same defensive concerns compelled the Allies to put better men into cryptology than the offense-minded Germans did. In Poland, the Biuro Szyfrów, looking far down the road of cryptanalytic need, hired mathematicians. In Britain, Cambridge students and graduates were the cream of the nation, and G.C.&C.S. took the cream of that cream. In the United States, the draftees who scored the highest on an IQ test were proposed for cryptologic work. But in Germany, no such recruiting seems to have taken place; the Germans, on a blitzkrieg of conquest, seemed not to feel that they needed codebreakers badly. With one or two exceptions, they brought in mathematicians for cryptanalysis only later, during the war. So their agencies, despite individually bright men, did not perform as well as did the Allied units.
The leaders of Britain and Germany personified these differing behaviors. Churchill eagerly read the intercepts and encouraged his cryptanalysts to continue laying their golden eggs. Hitler, although he accepted intercepts, never visited any of his cryptanaltic agencies, never thanked them, and never showed any special interest in their output. In part this difference stemmed from the two nations’ different immediate needs: for a long time, Churchill had little more than intelligence, while Hitler was conquering Europe. In part it was a matter of background: Churchill had for decades dealt intimately with the results of codebreaking, Hitler had never done so. And in part it reflected long-standing national policies. Britain’s maintenance of the balance of power is a reactive or defensive technique that requires intelligence to succeed. Germany utilized the strategic offensive to resolve her problems of indefensible borders and severe domestic tensions. But this does not call for intelligence, and so her leaders interested themselves in it less than Britain’s leaders did.
Another basic reason for the superiority of Allied cryptanalysis lay in the rule of law. This proved more efficient than a dictator’s whims. Agreement on impersonal norms permitted both Britain’s and America’s high commanders to centralize and rationalize their cryptologic efforts instead of competing for the power that knowledge confers. At Bletchley, the concentration of effort let the various huts share knowledge and bombes and find kisses. In Washington, the army and navy, despite some friction, divided up their work. In Germany, on the other hand, seven major codebreaking agencies continued to work separately at least in part because the organizations of which they were part—among them the army, the Armed Forces High Command, the Foreign Office—were fighting for access to Hitler. He wanted that arrangement because it remitted power to him. But this fragmentation spread cryptanalytic manpower very thin and deprived the agencies of the benefits of cooperation. Parliamentary authority, more rational, prevented such a situation from arising in Britain or the United States.
Two other reasons, of a far less fundamental nature, also conduced to Allied superiority. First, since Germany used a single cryptosystem very extensively, the Allies could concentrate more manpower on it, had more intercepts in it to work on, and looked forward to greater rewards from solving it than if they had to work on many systems of several nations, as the Germans did. Second, the Allies ruled the sea. They thus could seize documents from enemy ships. The Germans captured only a few Royal Navy cryptographic documents.
One day during the war, a can of Spam appeared on the table of Leonard Forster, a translator in Hut 4. “Look,” said his wife, “here’s this new thing that’s come from America.” When he saw the can, Forster felt a great swelling of pride. For he had had a hand in getting that food to Britain.
ULTRA had helped bring food to his table and to millions of others in Britain. It was one of the great intellectual achievements of the century, no less remarkable because it was achieved against a secret produced by men rather than one of nature. The unraveling of the Enigma was the equivalent of those endeavors that are awarded Nobel prizes. And, like those, it benefited humankind.
By bringing peace closer, ULTRA shortened the time that fathers were separated from their children, husbands from wives. And it spared an untold number of people—men in the cargo ships and their escorts; men at the fighting fronts; men, women, and children under the bombs in the cities of the home fronts. That was ULTRA’s greatest gift: it saved lives. Not only British and American lives, but German lives as well. That is the debt the world owes the Bletchley codebreakers; that is the crowning human value of their triumphs.
APPENDIX:
ENCIPHERING WITH NAVAL ENIGMA
PREPARING TO ENCIPHER A MESSAGE IN NAVAL ENIGMA WAS A complicated and multistep procedure. It required an indicators book, which listed groups of three letters to specify a particular key net, that month’s machine-setting list, which gave each day’s settings, tables to encipher pairs of letters into other pairs, and other papers.
The first steps, preparing the so-called “inner settings,” could be done only by an officer. He would do the following:
1.
Select from the eight rotors available the three that the machine-setting list specified for that day.
2.
On each rotor, turn the alphabet ring to the position prescribed in the machine-setting list and lock it in place with the pin.
3.
Assemble the rotors on their shaft in the order prescribed by the machine-setting list and insert them into the machine.
The radioman would then prepare the outer settings. He would:
1.
Turn the rotors until the three letters specified in the machine-setting list appeared in the windows of the machine’s closed lid.
2.
Insert the plugs at both ends of the plugboard cables into the proper sockets of the plugboard to connect the pairs of letters prescribed by the machine-setting list.
The radioman next readied the message key. He would:
1.
Determine the key net on which the message is to be set.
2.
In the distribution list in force, find the numbers of the columns in the indicators book assigned to that key net.
3.
From one of those columns, pick out at random a three-letter indicator.
4.
Write this key-net indicator in the last three cells of the first line of the encipherment form’s book-group column (perhaps called that because for some years the German plaintext was encoded in the Allgemeines Funkspruchbuch before being enciphered in Enigma).
5.
Make up a dummy letter at random (a null) and write it in the first cell.
6.
In the indicators book, pick out at random any three-letter indicator.
7.
Write it in the first three cells of the second line of the encipherment form’s book-group column.
8.
Make up a null at random and write it in the last cell of that line.
9.
Determine the bigram table in force from the key list.
10.
Combine the letters of the first cells in the first two lines into a vertical pair.
11.
Look up the vertical pair in the bigram table and replace it with its cipher pair.
12.
Write the two letters of this cipher pair horizontally into the first two cells of the first line of the radio-group column of the encipherment form.
13.
Repeat this process with the three remaining vertical pairs in the book-group column, writing them horizontally into the first two lines of the radio-group column.
14.
Press, on the Enigma keyboard, the three letters of the original, unenciphered key-net indicator and write down at the top of the message form the letters lit up on the illuminable panel (this becomes the message key).
15.
Turn the rotors until the letters of the message key show in the lid windows.
A naval Enigma encipherment worksheet. The cipher clerk would write the plaintext in the right-hand column under the heading Bedeutung (meaning). The first word, Wespe, is a priority indicator. The message begins, �
�Leipzig an Flotte. Köln Standort Norderney Leuchtturm …” (Leipzig to the fleet: Cologne location Norderney lighthouse …). The clerk would then follow the instructions for choosing and enciphering the indicators and finally for enciphering the plaintext. Translations, beginning at the left-hand column: Anfangskenngruppen, beginning indicator groups; Verschlüsselt mil Schlüssel M, enciphered by Enigma; Endkenngruppen, final indicators groups; Uhrzeitgruppe, time group; Gruppenzahl, number of groups; Funkgruppen, radio groups; Buchgruppen, book groups; Spruchschlüssel, message key; gültig für 3.8., valid for August 3; Schlüsselkenngruppe, key-net indicator; Verfahrenkenngruppe, message-grade indicator (but actually a random group).
Part of a page of a Kennbuch, or indicators book, showing the random three-letter groups that form part of the Enigma key. A deciphering portion has the indicators in alphabetical order with their column numbers next to them.
A portion of a bigram table, which serves to encipher part of the Enigma key.
A portion of a key list for the commercial Enigma used by German forces in the Spanish civil war. For each day it shows, under Innere Einstellung (inner setting), the positions for the three removable rotors in Roman numerals and the alphabet ring settings for the three removable rotors and the reversing rotor. Under Ausseneinstellung (outer setting), it gives the rotor positions for the start of encipherment of each message sent during two periods of the day.
A distribution list for the indicators book. It shows, for example, that the three-letter indicators in columns 81 to 140 of the book are to serve as key-net indicators for the TRITON key net, used by Atlantic U-boats. Indicators from other columns specify other key nets.
The cipher clerk would then write the plaintext into the book-group columns of the cipher form without word breaks but with x or y to separate sentences. He replaced the common letter-pairs ch and ck with q. Priority indications, such as SSD (for sehr sehr dringend, very very urgent), would be replaced by a variety of words, such as Wespe. Ready at last for the actual encipherment, he would summon a colleague. As he pressed the successive letters of the plaintext on the typewriter keyboard, his co-worker would write down in the radio-group columns of the form the letters that lit up on the illuminable panel—the letters of the cryptogram, the secret message that was to be sent. The cipher clerk would cross out the book-group column to avoid its being transmitted by mistake. He would transmit the enciphered indicators before the enciphered message. At the other end, the recipient would decipher the indicators, recover the message key, and translate the message.
The system was enormously complex. But it was formidably strong.
In addition, two kinds of messages were encoded for brevity before being enciphered in Enigma. U-boat sightings and other reports were condensed into four-letter groups by the Short Signal Book. Weather reports converted measurements into single letters using tables in the Short Weather Cipher. Thus, in Table 3 of the edition in use in 1941, atmospheric pressure of 971.1–973.0 millibars was represented by N, 973.1–975.0 by M. In Table 6, cirrus cloud cover of 1/10–5/10 became E. Using the Short Weather Cipher, the observer aboard ship converted his measurements into letters in a prescribed order. For example, a surface observation from 68° north latitude, 20° west longitude (northwest of Iceland) reporting atmospheric pressure of 972 millibars, temperature of minus 5° Celsius, wind from the northwest with force 6 on the Beaufort scale (a strong breeze of 25 to 31 miles per hour), 3/10 cirrus cloud cover, and visibility up to 5 nautical miles, would become MZNFPED. To this would be appended the two-letter signature of the reporting ship.
Part of a page of the Short Signal Cipher of 1941. This page deals with plans for attacking. Each four-letter group replaces a phrase. Thus aabb stands for “Intend to attack reported enemy forces in naval square …” The encoding shortens the message to be enciphered and provides an extra layer of secrecy.
Part of a page of the 1942 edition of the Short Weather Cipher, the edition captured from the U-559. In each table a letter replaces a meteorological observation. In Table 11, air temperature in whole degrees centigrade, 21° becomes h in the sequence of letters to be enciphered. Table 12 (not shown here) lists differences between air and water temperatures, and Table 12A (not shown here) the time of the weather observation.
A drawing from Arthur Scherbius’s U.S. initial patent for the Enigma. Figure 1 shows the typewriter keyboard (1), the input plate (4), the rotors (6, 7, 8, 9), and the output (12), here a perforator for a teletypewriter paper tape. There is no reversing rotor; the current goes through the rotor sequence only once.
A side elevation of an Enigma machine, from Willi Korn’s patent for adding notches to each rotor’s alphabet ring to vary the advancing of the adjacent rotors.
The route of the electrical current in the Enigma, as shown in a German navy manual. Umkehrwalze, reversing rotor; Drehbare Schlüsselwalzen, turnable rotors; Eingangswalze, entry rotor.
Part of the North Atlantic portion of the German navy’s grid of the world’s oceans. The chart is divided into approximate squares designated by pairs of letters, and each square is subdivided into smaller squares designated by pairs of numbers. The numbered squares could be further subdivided into smaller numbered squares for greater precision in location.
NOTES
THE FOLLOWING ABBREVIATIONS ARE USED IN THE NOTES:
ADM Admiralty series, PRO
CLKE Clarke Papers, Churchill College, Cambridge
DEFE German naval intercepts, PRO
DENN Denniston Papers, Churchill College, Cambridge
FO Foreign Office Papers, PRO
MA Militärarchiv, Freiburg-im-Breisgau
M.Dv. Marinedienstvorschrift (naval regulation)
NA National Archives, Washington, D.C.
PG German naval documents captured by the British
PRO Public Record Office, London
RG Record Group, NA
RM Naval documents, MA
WK Wehrkreis (army documents), MA
Data on times of solution come from DEFE 3, which gives for each intercept the date and time of interception and the date and time of its dispatch to the Operational Intelligence Centre. The difference is called the solution time, which includes translation.
Figures for tonnage sunk come from Roskill, War at Sea, 1:615–16, 2:485–86, 3:388–89; Morison, 1:410–411, 10:365; and Rohwer, Axis Submarine Successes, All are in gross tons (sometimes called gross register tons), not deadweight tons or displacement tons.
1. A Staff School Memory
Unless otherwise specified, all information in this chapter comes from ADM 1/11133; PG 30106; Roskill, Secret Surrender; and interviews with Baker-Cresswell, Balme, and Wilde.
PAGE
2
James Roosevelt: New York Times, May 10, 1941.
2
OB series: Rohwer, Axis Submarine Successes, 321.
4
Asdic: Hackmann.
4
radar errors: Kemp interview; RM 7/104:87; MacLachlan, 112; Rohwer, “La radiotélégraphie.”
6
less than 70 days: Hinsley, 1:163, 337.
6
two days before the attack: DEFE 3:1:2TP368.
6
126,000, 249,000: Roskill, War at Sea, 1:616.
6
rationing hurting, thinking with stomachs: Leonard Mosley, Back to the Wall: The Heroic Story of the People of London During World War II (New York: Random House, 1971), 225.
6
meat, cheese rations: Great Britain, Ministry of Food, How Britain Was Fed in War Time, 58.
6
31 million tons: Winston S. Churchill, Secret Session Speeches, ed. Charles Eade (New York: Simon and Schuster, 1946), 38, 49–50.
6
28 million tons: Schoenfeld, 126.
16
“Is there a chance”: Baker-Cresswell interview.
2. The Wreck of the Magdeburg
All details about the Magdeburg grounding, salvaging attempts,
and code-book jettisoning are from Assessor Tolki’s report of Sept. 17, 1914, in PG 64859; Makela; Germany, Marine-Archiv, Ostsee, 1:76–85. Details of bringing the codebook to Britain are from Count Constantine Benckendorff, Half a Life: The Reminiscences of a Russian Gentleman (London: Richards, 1954); ADM 53/62801; FO 371/2095:490–509; Hammant.
17
Magdeburg specifications: Gröner, 1:172, 175.
21
fourth lay hidden: The accounts in Tolki’s report in PG 64859 mention only three codebooks aboard the Magdeburg—those in the steering room and radio shack and on the bridge. All were said to have been burned or jettisoned. Makela, p. 49, lists the serial numbers of three codebooks: 145, 151, and 974. Both sources thus imply that only three books were aboard the cruiser. But the book sent to the British, 151, now in the Public Record Office as ADM 136/4156, shows no signs of immersion. It thus could not have been one of the three mentioned in PG 64859. The Magdeburg therefore had to have had four codebooks. Why is the fourth not mentioned in the sources? Because the crew members did not know about it, forgot it, or suppressed their knowledge of its existence in their testimony, while the serial number of one of the other three was not recorded or was lost. This seems to me more likely than the only other explanation that would account for No. 151 being captured dry: that it was left in the steering room, on the bridge, or in the radio room by Bender or Szillat or Neuhaus, who then, to avoid punishment, lied about throwing it overboard or burning it, while Galibin, to brag, lied about finding the codebook in the captain’s cabin, it really having been found elsewhere by him or another Russian. Makela’s statement, p. 49, that the codebook on the bridge was not destroyed is contradicted by the statement on the next page that that codebook was jettisoned.
