In September 2005, Canada's former Foreign Service Communicators held a reunion in Ottawa. Foreign Affairs Canada kindly loaned some materials and exhibits for use during the reunion. These vintage "tools of the trade" are illustrated below along with explanations of their development and use.

By David Smith

          One-time Figure and Letter Pads (OTFP/OTLP)
OTFP and OTLP were the successors to systems such as the Government Telegraph Code (GTC).  GTC was a low-level restricted document, similar to OTFP where one simply looked up the desired word and wrote down the corresponding code.  The real purpose was a means of saving on words and thus commercial cable costs. GTC was the forerunner and basis for the idea of an OTFP cypher. An interesting aside is the story of when Morse code operators had to transmit Chinese characters. With 10,000 characters in existence, (most Chinese I discovered during an assignment in Beijing knew only 2,000 to 4,000 characters),  operators needed a means of converting the Chinese characters to Morse.

Numbers from 000 to 9999 were assigned which meant the originator had to convert to numbers while the recipient had the task of converting back to characters.  I watched this process in Beijing when commercial cables were delivered to the Canadian Embassy and our local Chinese staff would do the converting back to Chinese characters – and then most likely to English for the Canadian staff.  Like GTC, OTFP was a completely manual encryption method used by External Affairs (EA) and others from the 1930’s until it was phased out in the 1980’s. In the beginning, EA used British code books and pads until the 1950’s when Canada began using “Canadian” Encode/Decode books and pads.  The first editions produced (numbers 001) are inscribed by the then Secretary of State for External Affairs, Lester B. Pearson, with the notation “Finally we have our own Cypher system”.

One time figure and letter pads had sealed edges. The seal was a soft plastic but rubbery membrane and the operator would only be authorized to unseal the page or pages required to encode or decode a particular message.  The lower right-hand corners of the pads were not sealed so the communicator could slip a double edged scribe (knife) into the open corner and slide it upwards and then to the left to cut open one page at a time.  Each page was numbered and this number, along with the serial number of the pad would be the first two five-figure numbers encoded to verify to the receiving operator which book and what page number was being utilized.  Where needed, zeros would be added to make up five figures. Line numbering was not used. A new page was required for each new message, regardless of the length.

Encode and decode pads were produced as “2-way” or “3-way” and multi-way within certain geographical areas, the UN, or Commonwealth countries.  2-way pads were used between External Affairs headquarters in Ottawa and one other mission (Embassy or High Commission).  Three-way encryption pads would allow use by two overseas missions. Most missions used two-way pads between their location and HQ. Pads were assigned either an “IN” or “OUT” designation. IN pads were used for decoding messages  and OUT pads were used for encoding messages.


OTFP/LP pads were serial numbered and tracked and inventoried very carefully. A crypto-custodian’s duties included verifying and acknowledging these pads including what pages in each pad had been used.  Pads were dispatched to missions via diplomatic courier and each shipment would require verification from the receiving mission.

The heart of the OTFP/LP coding system were two code books – Yellow for Encode and Red for Decode.  These books were the products of some very sharp minds.  Simply put, these books provided the means for assigning almost every word needed with a 4 figure code.  If for example, the word “TO” was required, the operator would simply look up the word TO under the T tab and select the 4 figure code. (For a word such as “TO” which was used regularly, there would be a selection of 4 figure codes). Other less-utilized words would have just one code.  Some 4 figure codes however could contain an entire phrase such as “grateful for immediate reply” or “full report to follow by bag”.  This 4 figure code word would then be pencilled underneath a line of pre-printed figures in the 2 way pad until the message was completed. What one ended up with was a pad full of lines of machine produced figures and another penciled line underneath entered by the communicator.  The last code word in a message would be “Message ends full stop” and I believe the code word was 4147.  The communicator now had to subtract the penciled entries from the machine produced lines above and the result would be typed onto a teleprinter producing a paper tape of Murray code figures.  The result could now be transmitted using a number of methods including commercial cable, telex, External Affairs line equipment or even Morse code. (Some countries used Morse  to communicate in the 1960’s).  One became very adept at subtracting on the fly.  The end result would look like this:

91157 29473 39760 28198 28999  41093 28741 38924 47938 98743

One line consisted of five groups of five-figure entries, two spaces and then another five groups per line.

For the receiving end, decoding could be straightforward providing the copy received was not corrupted.  Where things could get interesting was when the copy had errors due to anything from a mathematical error or a hit on the line during transmission or a relay operator keying in the wrong morse code.  A corrupted five figure group would not prevent the majority of the message from being decoded but sometimes one had to guess or simply pen an entry “2 groups corrupt” or a similar notation into the decoded plain-language version. There were a variety of unique ways to work on a corrupt group and old-timers in the business would not give up lightly.

An inquiring mind might wonder how the encode/decode books would handle a word like onomatopoeia.  For words that were not listed in the books, one could simply “Spell a word of X letters”.  The books covered every possibility, including acronyms and shortened versions of titles.  Most OTFP messages were very short, from a few lines to one page at the most. Longer correspondence was sent via diplomatic bag.

At one point in time, before the introduction of electrical/mechanical cypher systems, OTFP was used extensively. It was very slow and incredibly laborious. A one page message could take two operators hours to complete. A former colleague tells the story of a mission he visited receiving a OTFP message of 600-700 groups. It took mission personnel almost 2 full days to decrypt and process it.  French words had to be spelled as the Encode/Decode books did not allow for any language other than English. Another colleague recalls receiving a telegram to be encoded with OTFP whereby the Ambassador insisted it be sent in French.  Needless to say, each and every word had to be spelled. Lovely!

The beauty of this One-time Figure Pad system was two-fold.  These messages were unbreakable without access to the pads and the coded teletype tape or a printed page of five figure groups was unclassified and could be seen by anyone. Indeed, as late as the 1960’s, communicators in some of External Affairs overseas missions did not have transmission facilities in the Embassy and would use the local PTT facilities. I recall one post in particular – Colombo, Ceylon where the communicator would produce the teletype tape from his office teleprinter and then call on a “boy” with a bicycle to deliver them to the local PTT offices for transmission to Canada. Such a system would undoubtedly pass through numerous relay points before finally arriving in the External Affairs Communications Centre of the Parliament building East Block. Each relay would be an opportunity for “altering” the original version and the end result would require some tricky decoding by the communicator in Ottawa. Sometimes a request for an entire repeat or a section of the message would be requested.    As secure as this system was, I doubt there was a dry eye amongst the communications group when OTFP was finally phased out in favour of faster and more efficient cypher systems.


One Time Letter Pads were quite different to that of One Time Figure Pad encryption methods. The pads for starters were much smaller and were blue in colour rather than yellow and red.  All that was required were the pads themselves. No basic code books were required. There was a smaller emergency two-way pad as well although I never saw them in use.  Other Canadian Government Departments also used a system of one-time pads for encryption of sensitive messages.

The double edged scribe (knife) at the left bottom was used to open the sealed pads. For the OTFP coding system, there were two code books – Yellow for Encode and Red for Decode. The blue book in the lower right corner is a One Time Letter Pad. (Photo by David Smith)

olfp_otlp_canadian _code_books1.jpg
Canadian Diplomatic Basic Books were used to encypher (OUT) and decypher (IN) messages  in conjunction with  the OTFP system. The encode book, normally a bright yellow when new, now looks like tan in this photo. CEA means Canadian External Affairs (Photo by David Smith)

olfp_otlp_diplomatic _courier.jpg
Tools of the Diplomatic Courier: At the left side are two lever locks The red bar in the center is sealing wax. At the right are waybills, an Embassy Brass seal, some baggage tags from the Hong Kong to Beijing run and the little red book is "Mao Tse-tung's Book of Thoughts". (Photo by David Smith)

A red diplomatic bag which was used for classified items such as crypto material and hand carried by couriers while a white diplomatic bag was used for unclassified items and was sent unescorted by air.  The tags used to be made from starched linen and the destination was either printed (mostly) or hand written (rarely).  A string would fix the linen tag to the neck of the bag.  Over the string would be tied a lead seal and a spike which would puncture the neck where the string was wound round the neck and then this would be crimped with a crimping tool making an impression in the seal of the mission that sealed it.   Where the string from the linen tag was knotted, a blob of melted sealing was would be dropped and then the Embassy brass seal would be pressed into the soft wax making another impression of the coat of arms and the name of the Embassy. It was an good system system but very tedious and time consuming. Seals were often placed on the back of envelopes as well.

In later years, we went to plastic lever locks which were simply a plastic case with the tag inside indicating the destination and the sender. The lever would go around the neck and snap into the case with the string far tighter (it could be adjusted) than one could tie them in the method above. To secure the lever, a small plastic tag with a random serial number would go and once the arrow-head of the tag was placed into the plastic case, it could not be removed without breaking it.  It was therefore easy to identify any tampering. The lower lever lock in the photo is simply an update and ostensibly, an improvement.

Bags were always canvas - very strong but not waterproof.  Bags are never out of the Couriers sight except while in flight. A courier is the first to disembark and the last to embark, normally sitting in the nearest isle seat next to the main door of the aircraft.

There are two items of interest in this photo. In the upper left corner is a programmable circuit board from a KG-30 .There were two boards per unit and they were set with a stylus according to a pad of settings.   Each end of the circuit had to be set identically otherwise synchronization would not be possible. The tube like object at the right side middle is a gummer. That is the instrument that was used stick the gummed decypher/encypher tapes from the Noreen or Typex devices.  It contained water and was tipped with a sponge. It wet the tape as one drew it through.  Above the gummer is a finger "tape cutter",  It had a little blade on one side for cutting the tape as it was gummed down line by line. (Photo by David Smith)

To see how some of these artifacts were used, select the  Canadian Diplomatic Courier.


1. The original 5 level Baudot code became known as the International Telegraph Code No. 1. Sometime around 1900, another 5-bit code called the Murray Code was invented. The Murray Code eventually displaced the Baudot Code and became known as the International Telegraph Code No. 2. Unfortunately, everyone was hopelessly confused by this time -- to the extent that Murray's name sank into obscurity, while Baudot's name became associated with almost every 5-bit code on the face of the planet, including the International Telegraph Code No. 2. (From

Credits and References:

1) David Smith <drdee(at)
2) Laurie Archibald  <laurie.archibald(at)> Retired External Affairs Communicator
3 John Roy- <john.roy3(at)>  Retired External Affairs Communicator

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Jan 1/05