Trench code
Encyclopedia
In cryptography
, trench codes were code
s used for secrecy by field armies in World War I
. A reasonably-designed code is generally more difficult to crack than a classical cipher
, but of course suffers from the difficulty of preparing, distributing, and protecting codebook
s.
However, by the middle of World War I
the conflict had settled down into a static battle of attrition, with the two sides sitting in huge lines of fixed earthworks fortifications. Vast numbers of men were sacrificed in futile offensives to break these lines, with the usual result being little more than a dent of a few kilometers at best. With armies generally immobile, distributing codebooks and protecting them was easier than it would have been for armies on the move. To be sure, trench-raiding parties could sneak into enemy lines and try to snatch codebooks, but then an alarm could be raised and a code quickly changed. They were changed on a regular basis anyway.
began to develop trench codes in early 1916. They started out as telephone
codes, implemented at the request of a general
whose forces had suffered devastating artillery
bombardments due to indiscretions in telephone conversations between his men. The original telephone code featured a small set of two-letter codewords that were spelled out in voice communications. This grew into a three-letter code scheme, which was then adopted for wireless, with early one-part code implementations evolving into more secure two-part code implementations. The British began to adopt trench codes as well.
started using trench codes in the spring of 1917, evolving into a book of 4,000 codewords that were changed twice a month, with different codebooks used on different sectors of the front. The French codebreakers were extremely competent at cracking ciphers
but were somewhat inexperienced at cracking codes, which require a slightly different mindset. It took them time to get to the point where they were able to crack the German codes in a timely fashion.
cryptology into the 20th century, publishing an influential short work on the subject in 1915. He was assigned to France in an administrative role, but his advice was eagerly sought by colleagues working in operational cryptology. Another Signal Corps officer who would make his mark on cryptology was Joseph Mauborgne
, who in 1914, as a first lieutenant
, had been the first to publish a solution to the Playfair cipher.
When the Americans began moving up to the front in numbers in early 1918, they adopted trench codes and became very competent at their construction, with a Captain Howard R. Barnes eventually learning to produce them at a rate that surprised British colleagues. The Americans adopted a series of codes named after rivers, beginning with "Potomac". They learned to print the codebooks on paper that burned easily and degraded quickly after a few weeks, when the codes would presumably be obsolete, while using a font that was easy to read under trench conditions.
The British
and French were already familiar with such problems in "communications discipline". They hadn't completely solved the problems either, but they had at least managed to get it through the heads of most of their signalmen that if they didn't have time to properly encrypt a message, they shouldn't bother trying; send the message unencrypted, or "in the clear". A partially or badly encrypted message could undermine a cipher or code system, sometimes completely, which made an unencrypted message far preferable.
Cryptography
Cryptography is the practice and study of techniques for secure communication in the presence of third parties...
, trench codes were code
Code (cryptography)
In cryptography, a code is a method used to transform a message into an obscured form, preventing those who do not possess special information, or key, required to apply the transform from understanding what is actually transmitted. The usual method is to use a codebook with a list of common...
s used for secrecy by field armies in World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
. A reasonably-designed code is generally more difficult to crack than a classical cipher
Classical cipher
A cipher is a means of concealing a message, where letters of the message are substituted or transposed for other letters, letter pairs, and sometimes for many letters. In cryptography, a classical cipher is a type of cipher that was used historically but now has fallen, for the most part, into...
, but of course suffers from the difficulty of preparing, distributing, and protecting codebook
Codebook
A codebook is a type of document used for gathering and storing codes. Originally codebooks were often literally books, but today codebook is a byword for the complete record of a series of codes, regardless of physical format.-Cryptography:...
s.
However, by the middle of World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
the conflict had settled down into a static battle of attrition, with the two sides sitting in huge lines of fixed earthworks fortifications. Vast numbers of men were sacrificed in futile offensives to break these lines, with the usual result being little more than a dent of a few kilometers at best. With armies generally immobile, distributing codebooks and protecting them was easier than it would have been for armies on the move. To be sure, trench-raiding parties could sneak into enemy lines and try to snatch codebooks, but then an alarm could be raised and a code quickly changed. They were changed on a regular basis anyway.
French Army
The FrenchFrance
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
began to develop trench codes in early 1916. They started out as telephone
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
codes, implemented at the request of a general
General
A general officer is an officer of high military rank, usually in the army, and in some nations, the air force. The term is widely used by many nations of the world, and when a country uses a different term, there is an equivalent title given....
whose forces had suffered devastating artillery
Artillery
Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...
bombardments due to indiscretions in telephone conversations between his men. The original telephone code featured a small set of two-letter codewords that were spelled out in voice communications. This grew into a three-letter code scheme, which was then adopted for wireless, with early one-part code implementations evolving into more secure two-part code implementations. The British began to adopt trench codes as well.
German Army
The GermansGermany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
started using trench codes in the spring of 1917, evolving into a book of 4,000 codewords that were changed twice a month, with different codebooks used on different sectors of the front. The French codebreakers were extremely competent at cracking ciphers
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
but were somewhat inexperienced at cracking codes, which require a slightly different mindset. It took them time to get to the point where they were able to crack the German codes in a timely fashion.
U.S. troops
The Americans were relative newcomers to cryptography when they entered the war, but they did have their star players. One was Parker Hitt, who before the war had been an Army Signal Corps instructor. He was one of the first to try to bring US ArmyUnited States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
cryptology into the 20th century, publishing an influential short work on the subject in 1915. He was assigned to France in an administrative role, but his advice was eagerly sought by colleagues working in operational cryptology. Another Signal Corps officer who would make his mark on cryptology was Joseph Mauborgne
Joseph Mauborgne
In the history of cryptography, Joseph Oswald Mauborgne co-invented the one-time pad with Gilbert Vernam of Bell Labs. In 1914 he published the first recorded solution of the Playfair cipher...
, who in 1914, as a first lieutenant
First Lieutenant
First lieutenant is a military rank and, in some forces, an appointment.The rank of lieutenant has different meanings in different military formations , but the majority of cases it is common for it to be sub-divided into a senior and junior rank...
, had been the first to publish a solution to the Playfair cipher.
When the Americans began moving up to the front in numbers in early 1918, they adopted trench codes and became very competent at their construction, with a Captain Howard R. Barnes eventually learning to produce them at a rate that surprised British colleagues. The Americans adopted a series of codes named after rivers, beginning with "Potomac". They learned to print the codebooks on paper that burned easily and degraded quickly after a few weeks, when the codes would presumably be obsolete, while using a font that was easy to read under trench conditions.
Communications discipline
However, American codemakers were often frustrated by the inability or refusal of combat units to use the codes—or worse, to use them properly. A soldier engaged in combat doesn't always feel the need to do things "by the book" even when there are very good reasons to do so, and generals on the front line felt that they had other things to worry about. One codemaker suggested that the best way to address the problem was to publicly hang a few offenders, but he lacked the authority to do so.The British
United Kingdom of Great Britain and Ireland
The United Kingdom of Great Britain and Ireland was the formal name of the United Kingdom during the period when what is now the Republic of Ireland formed a part of it....
and French were already familiar with such problems in "communications discipline". They hadn't completely solved the problems either, but they had at least managed to get it through the heads of most of their signalmen that if they didn't have time to properly encrypt a message, they shouldn't bother trying; send the message unencrypted, or "in the clear". A partially or badly encrypted message could undermine a cipher or code system, sometimes completely, which made an unencrypted message far preferable.