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NL TNO
Electronic on-line telex encryptor
Cryptauphyl 1
was an electronic tapeless/rotorless cipher machine (TROL) 2
for on-line and off-line encryption and decryption of
telegraphy signals (telex),
developed between 1960 and 1962 by the State Defense Organisation
of the Applied Physics Laboratory (RVO-TNO, now: TNO) in The Hague (Netherlands) [1].
The first incarnation of the device could be broken by the
Dutch cipher authorithy NBV (NLNCSA, now part of AIVD)
with no more than 1200 characters of ciphertext [2].
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Cryptauphyl was developed as part of a national and international race
under the name TROL,
to develop electronic alternatives for the ageing
rotor machines of the
previous two decades, such as the well-known Enigma,
the Hagelin pin-and-lug machines and NATO's
eight-rotor KL-7.
Cryptauphyl is first described in a
confidential memorandum of RVO-TNO,
which was submitted in November 1960 to the NVBR, the
National Communications Security Council. From this, we learn
that the device has a fully transistorised key generator with traffic flow
security (TFS).
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Strangely, and perhaps erroneously, the description claims that the characters
generated by the key generator have a Gaussian distribution [1]. Clearly,
this cannot be the intention when developing a secure cipher machine,
for which one would expect a uniform distribution.
This was likely a misinterpretation of the person who wrote the
description, as the NBV
later reports in a memorandum that Cryptauphyl's frequency distribution
was within reasonable boundaries [2].
It is known that Cryptauphyl was a self-synchronising cipher machine,
also known as autoclave, based on linear feedback shift registers
(LFSR) [3]. An autoclave allows late-entry communication without additional
synchronisation, but is often prone to error propagation in case of
interference. Furthermore, the use of LFSRs makes the cipher susceptible
to codebreaking.
This was known by the NBV however, and adequate proposals for the
addition of non-linear operations were suggested, both by the NBV and by
Professor Oberman of Delft University.
It can be assumed that such nonlinear improvements were implemented in a
later incarnation of Cryptauphyl.
From the minutes of the TROL-commission of the NVBR, it seems likely that
four different prototypes were made by TNO over the course of 1961 and 1962,
each successive one with further improvements.
It is currently unknown whether the machine was ever produced in any reasonable
quantity, but for several reasons this seems very unlikely:
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- Due to a contract between Philips and the Dutch State, 3 series production would only have been possible at Philips at the time. No such production is known.
- The Dutch Government chose Ecolex V, the TROL design from Philips (rather than Cryptauphyl), for submission to NATO's TROL-evaluation in July 1962.
- RVO-TNO withdrew Cryptauphyl from NATO's TROL-evaluation in mid-1962 [10].
- Cryptauphyl-inventor Rudolf Slegtenhorst left RVO-TNO in 1963 to become director at the Reactor Institute of Delft University [11].
- None of the mandatory documents for approval, commissioning and decommissioning, exist in the archives of the NBV. Even for domestic or diplomatic governmental traffic, approval of the NBV was (and is) mandatory.
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Cryptauphyl is an acronym for
Cryptographic Automatic Physics Laboratory.
Also written as CryptauPhyl and – erroneously – as Cryptophyl,
Cryptophil or Cryptofiel.
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Not to be confused with other machines that were developed for NATO's
TROL evaluation, such as the Philips Ecolex V, the British
ALVIS (BID/610), the Philips Tarolex,
the Philips Ecolex X
and the TROL designs from foreign manufacturers.
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Due to a contract between PTT (acting on behalve of the Dutch State) and Philips,
signed in September 1957, production of cipher machines had to be given to
Philips.
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CLASSIFIED —
At present we are unable to show a picture of Cryptauphyl, as its
developer – TNO – has repeatedly refused to release information
about this device, stating that it is still state secret (after 60+ years),
claiming that it was in use until 1992. This seems very unlikely however,
as there are no approval documents in the archives of the Dutch cipher authority
NBV ( NLNCSA). It is also known that the final design of a TROL system
was not TNO's Cryptauphyl,
but rather the Philips Ecolex V — with input from
Oberman & Snijders —
which was cryptographically incompatible with the TNO design.
The Ecolex V later evolved into the Philips Tarolex
and finally the Philips Ecolex X.
Since detailed technical descriptions of the latter two systems exist in the public domain,
including on this website,
the secrecy surrounding Cryptauphyl – which is of 1961 vintage – does not hold.
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Advantages
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- Self-synchronising (autoclave)
- Late-entry synchronisation
- Traffic Flow Security (TFS)
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Disadvantages
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- Weak encryption algorithm
- Prone to error propagation
- Recognisable ciphertext format
- Low data rate
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Post-WWII developments
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In the period following World War II, the
Dutch Government and the Royal Netherlands Army used a variety of cipher machines
for protecting confidential communications, including the
German Enigma Model G31,
the Hagelin BC-38 and C-446, and several
hand methods. But as these systems were known to be weak, the Dutch Government asked
the Dr. Neher Lab — the national laboratory of the
Dutch Post Office (PTT) — to develop a secure system for
diplomatic traffic.
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Despite their advantage as being unbreakable, OTT systems also have several
disadvantages.
The key needed for encryption of a message, must be at least as long as the
message itself, and can only be used once. Consequently, large quantities of
key tapes had to be distributed well in advance of sending a message. In practice,
the distribution of the bulky key tapes was a logistical nightmare,
which was undesired in times of crisis. To counter this, self-permuting
systems were promoted, in which the (random) key tape is replaced
by a so-called key generator — an electronic system that produces a long
pseudo-random sequence of uniformly distributed numbers, seeded by a
relatively short initial number of fixed length, which is known as the secret key.
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Individual TROL developments
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In those days, self-permuting cipher machines were also known as
Tapeless Rotorless On-Line (TROL), referring to the departure from the previous
generation of rotor-based machines
like the Enigma,
that were only suitable for off-line traffic and were cumbersome in operation.
In the late-1950s, the Dutch Government expressed an interest in a TROL-based
cipher system, after which several parties began developing a potential candidate.
TROL systems were developed independently by RVO-TNO,
Philips Usfa and two people from Delft University:
Professor Roelof Oberman and Anton Snijders.
At this point, Philips had already taken over development from PTT,
and Oberman and Snijders had left PTT to persue a career at Delft University.
Cryptauphyl was TNO's candidate, for which two patents
were filed, listing Rudolf Slegtenhorst as the inventor [I...X].
All parties submitted their design to the NBV, but from an NBV
memorandum of 31 May 1961, it becomes clear that
none of the designs were cryptographically strong enough [2].
The Oberman-Snijders design could be broken with 15,000 characters of
ciphertext, whilst just 1200 characters were needed to break TNO's
Cryptauphyl [2]. Furthermore, Cryptauphyl appeared to be prone to error
propagation, due to the fact that it was essentially an autoclave.
The Philips design was no better, as one text (with a weak chosen key) could
be broken with just 154 characters of ciphertext, whilst a second one
(with a stronger key) gave in after no more than 3000 characters.
The NBV concluded that the Oberman/Snijders design could easily be improved
by adding extra non-linearity, for which both Oberman & Snijders
and the NBV developed an appropriate solution.
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The TROL-commission
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Similar initiatives for the development of TROL equipment had meanwhile been
launched in the US, UK, Germany and France, all of which were potential candidates
for the forthcoming NATO evaluation 'TROL'. If the Netherlands wanted to
participate in the evaluation, the individual efforts somehow had to be combined,
as the deadline was nearing. In order to speed things up, a special
TROL-commission was founded under supervision of the NVBR.
The first meeting of this commission took place on 1 June 1961 at the
Ministry of Foreign Affairs in The Hague [3].
Present at the meeting were representatives of the NVBR,
its executive organ NBV, the state-owned laboratory RVO-TNO,
Philips Usfa and Delft University
(i.e. Oberman and Snijders).
The formentioned memorandum of 31 May 1961 [2]
was discussed, and it was suggested that the Oberman/Snijders
solution was the best way forward, provided that extra non-linearity –
as developed by NBV's Fred Hafkamp – was added to the design. 1
Philips could then use the design for its forthcoming
Ecolex V in which the TROL key generator was used as an add-on
for a modified Ecolex IV.
The image on the right shows an intermediate design of
the Ecolex V, with the Tarolex key generator at
the bottom right.
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At the second meeting of the TROL-commission on 9 June 1961, all
parties agreed with the proposal of the NBV, that the best way forward
was to use the Oberman/Snijders key generator in the
Philips Ecolex V.
It became clear however, that TNO was reluctant to abandon its Cryptauphyl
design and that they would proceed with its development independently from
the group [4]. At the third meeting of the commission, on 11 July 1961,
Philips indicated
that they could not wait for the group to come up with a final design,
if they wanted to meet the NATO deadline. Consequently, it was decided
that each of the parties would further develop its own TROL design,
with input from the NBV, and that NBV approval was required for
submission of a design to NATO.
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Adequate improvements with additional non-linearity had also been proposed by
Oberman and Snijders, but eventually Hafkamp's solution was chosen as it
was simpler to implement.
Hafkamp was an autodidact crypto expert, who had developed his own terminology.
In his notes, he describes the addition of non-linear operations as
irregular replacements [2]...[5].
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Philips improved its TROL design by increasing the complexity of the
key generator, including the addition of non-linear operations as
suggested by the NBV, probably with help from Oberman & Snijders,
and Hafkamp of the NBV. In mid-1962, TNO informed the NVBR
that it had withdrawn its Cryptauphyl from the NATO-evaluation, but that
its developement would be continued [10].
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In July 1962, Philips submitted its final
Ecolex V design
to NATO for aproval by SECAN. It passed all tests, but eventually
lost the evaluation to the British ALVIS (BID/610),
in what was thought to be a policial decision.
At Philips, the TROL development was initially
terminated, but was revived in 1966 when the need arose once again for
a self-permuting system for the Dutch Army, for which Philips
proposed the all new Ecolex X.
As development for the proposed Ecolex X would take
too long, it was decided to revive Ecolex V
as a gap-fill solution. After all, Ecolex V
was in a nearly finished state and allowed Philips to come up
with a 'new' and approved system in less than a year.
Furthermore, it allowed the existing Ecolex IV OTT
cipher machines to be reused.
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Although initially designated Ecolex V,
it was renamed Tarolex 19" 1
in December 1962.
Tarolex was introduced in 1967 and a total
of 151 units were built. It solved the
Army's immediate problem, but was still a gap-fill solution.
The device was large and heavy and had to be used in combination with
the existing bulky Ecolex IV
one-time tape machine, which had to be modified for connection to
Tarolex. Immediately after the
Tarolex machines had been delivered,
Philips started development of the projected
Ecolex X.
The latter was introduced in 1972 and carried many properties of the
original TROL and Tarolex principles, albeit
in a modernised form.
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The name Tarolex was derived from Tapeless Rotorless
On-Line encryption device ('ex'), which is basically the same
as TROL, but is more in line with Philips' naming conventions
like Ecolex, Satcolex, etc. Tarolex was initially used as
the name of one of the three TROL components,
but was later used for the entire system in the form Tarolex 19" or
Tarolex II, which was eventually shortened to Tarolex.
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What happened to the Cryptauphyl design remains unclear.
At the second meeting of the TROL-commission, TNO had made it clear
they they would continue to cooperate with the other parties, but
that they would also continue to develop Cryptauphyl [4].
TNO expected to have a first lab version in late 1961, at which
point they would have fulfilled the government's order.
It was then up to the Minister of Defense to decide which
TROL-design would be submitted to NATO.
In that case, prototypes were expected to be delivered in the first
half of 1962.
TNO had made it clear though, that Cryptauphyl would not be suitable for
use as an add-on to the Philips Ecolex IV [4].
TNO later informed the NVBR that it would not submit Cryptauphyl
for evaluation to NATO, but that they would continue its development
[10].
TNO had initially filed two patents related to the design of Cryptauphyl:
one on 2 February 1961 for a
pseudo random number generator,
and one on 31 May 1961 for a
complete encryption system (NL 107,306).
The first one was probably abandonned
as it is not available from the Dutch Patent Office (2025)
and the application number has been reused. In any case, both patents were
filed in several other countries the following
year, in May 1962 [I-IV and VI-X],
which confirms TNO's intention to further develop the device.
It is likely though that its development was eventually terminated,
as in 1963 Cryptauphyl-inventor Rudolf Slegtenhorst left TNO
to become director at the Reactor Institute at Delft University [11].
Whether Cryptauphyl was ever taken into production remains to be seen.
TNO insisted that its self-synchronising
feature (autoclave) was a unique selling point as it allowed late-entry
communication. However, such systems generally give rise to
error propagation, which for Philips and the NBV had been a reason
to reject the design.
It is certain though, that Cryptauphyl was not used by the Dutch Government
(in casu the Dutch Army), as in that case the mandatory approval of the
NBV would have been required, and no approval document exists
in the NBV archives.
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Descendants of the TROL development
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Cryptauphyl was part of a family of devices that were developed at TNO
between 1960 and 1966. The other family members do not serve any cryptographic purpose,
but are used for processing 5-bit digital telegraphy (telex).
The following devices in this family are currently known [6]:
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Punchrophyl 1960 Telex interceptor/recorder (paper tape) [7] Cryptauphyl 1960 Telegraphy encryption device (TROL) Scribophyl 1961 Printing device for (foreign) telex messages [8] Pluto 1966 Radio telex message registration system
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At present we have no further information about Cryptauphyl, other than wat
is presented on this page. We are looking for additional information that
may help us to expand this page, such as photographs, technical descriptions,
circuit diagrams and personal accounts of people who have worked with the
device or with any related equipment. If you can help,
please ➤ contact us.
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Device Self-permuting encryption/decryption device Purpose Online telex encryption, one-time key creation Category Tapeless, rotorless, on-line (TROL) Name Cryptauphyl Inventor Rudolf Slegtenhorst Manufacturer RVO-TNO, Physics Lab Development 1960-1962 Year - Country Netherlands Algorithm Proprietary autoclave Alphabet 32 (ITA-2), 26 (A-Z) Speed 400, 800, 1600 cpm Interface 20/40 mA, 60 V, single/double current Power ? Dimensions ? Weight ? Quantity 4 (prototypes only)
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Dutch patent application 260,780
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- Belgian Patent BE 613,307
Nul-één generator
RVO-TNO, filed 31 January 1962, priority 2 February 1961. 1
- German Patent DE 977,938
Schaltungsanordnung zum Erzeugen von Impulsfolgen mit statistisch verteilen Impulsen
Rudolf Slegtenhorst for TNO, 2 February 1962, priority 2 February 1961.
Published 26 July 1973.
- French Patent FR 1,605,102
Générateur produisant une série quasi-arbitraire de zéros et d/uns
RVO-TNO, filed 1 February 1962, priority 2 February 1961.
Published 16 March 1973.
- British Patent GB 1,298,451
Generator producing a quasi random series of zeroes and ones
RVO-TNO, filed 31 January 1962, priority 2 February 1961.
Published 6 December 1972.
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The original Dutch patent (with application number 260,780) is not available
in the Dutch Patent Office's database. It is likely that it was an
abandoned patent, as the application number was later resused.
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- Dutch Patent NL 107,306
Stelsel voor geheime berichtgeving
Rudolf Slegtenhorst for RVO-TNO, filed 31 May 1961 as NL365,358.
Published 15 April 1969.
- Belgian Patent BE 618,271
Stelsel voor geheime berichtgeving
RVO-TNO, filed 29 May 1962, priority 31 May 1961.
Published 19 September 1969.
- German Patent DE 977,777
Mit Binaerkodierung arbeitende Anordnung zur Verschluesselung von Nachrichtensignalen
Rudolf Slegtenhorst for TNO, 31 May 1962, priority 31 May 1961.
Published 26 March 1970.
- Danish Patent DK 108,615
Alæg til hemmelig kommunikation
Rudolf Slegtenhorst for TNO, 1 June 1962, priority 31 May 1961.
Published 8 January 1968.
- British Patent GB 1,172,971
Secrecy Communication System
TNO (NL), files 29 May 1962, priority 31 May 1961.
Published 3 December 1969.
- Norwegian Patent NO 113,572
Kommunikasjonssystem for Overfoering av Hemmelige Meldinger
Rudolf Slegtenhorst for TNO, 30 May 1962, priority 31 May 1961.
Published 13 February 1970.
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- Memorandum Eigenschappen Cryptauphyl
Memorandum Cryptauphyl specifications (in Dutch language). 1
RVO-TNO, Physisch Laboratorium, 25 November 1960. CONFIDENTIAL.
- MEMORANDUM betreffende de huidige stand van de Nederlandse ontwikkeling
op het gebied van zelfsleutelende electronische vercijferapparatuur
NBV, 31 May 1961. GEHEIM (SECRET).
- Verslag technische werkgroep TROL, 1 June 1961
Report of the technical committee TROL (Dutch).
NVBR, 16 June 1961. GEHEIM (SECRET).
- Verslag technische werkgroep TROL, 9 June 1961
Report of the technical committee TROL (Dutch).
NVBR, 26 June 1961. GEHEIM (SECRET).
- Verslag technische werkgroep TROL, 11 July 1961
Report of the technical committee TROL (Dutch).
NVBR, 24 July 1961. GEHEIM (SECRET).
- Museum Waalsdorp, Cryptografie/vercijfering
Accessed December 2023. 2
- Vastlegging telexberichten met de PUNCHROPHYL (1960)
Museum Waalsdorp. Retrieved December 2023.
- Printing (un)coded telex messages with the SCRIBOPHYL (1961)
Museum Waalsdorp. Retrieved December 2023.
- Maarten Oberman, Personal correspondence
November 2023 — August 2025.
- Minutes of meeting of the NVBR
Withdrawl of Cryptauphyl for NATO TROL evaluation. 3
- Rob Slegtenhorst (son of Rudolf Slegtenhorst)
Personal correspondence, 14 September 2025.
- Oberman et al., Drie ambitieuze Nederlandse cryptosystemen die strandden
Three failed Dutch encryption systems (1955-1965) (in Dutch language).
Maarten Oberman, Paul Reuvers and Marc Simons.
Historiek, 27 September 2025.
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Document released by Nationaal Archief (NA), obtained via Karl de Leeuw (CM304347).
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All references to Cryptauphyl, including a photograph that was attributed
to the device, have since been removed from the website.
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Partly declassified by AIVD.
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© Crypto Museum. Created: Tuesday 23 January 2024. Last changed: Tuesday, 30 September 2025 - 13:16 CET.
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