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USA
US ciper machine
- not in collection
- this page is a stub
KW-26, codenamed Romulus,
was the first fully electronic
teleprinter cipher machine,
developed between 1952 and 1957
by the US National Security Agency (NSA)
in cooperation with Burroughs Corporation Research Center.
It was the successor to the British 5-UCO.
From 1957 onward, more than 15,500 units were produced.
The device was built with ~ 50 valves (tubes)
and more than 800 BIMAG magnetic core logic units. It used an
algorithm that was based on Fibonacci shift registers.
In the mid-1980s, the machine was gradually replaced by the much smaller
KG-84.
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The KW-26 was a fairly large and heavy unit, but compared to its
predecessor, the British 5-UCO, it was relatively small.
The image on the right shows a single KW-26 unit, taken from a photograph
published on the CIA website [5].
For a full duplex communication link, two such units were required.
Note that the units used for transmission (TX) and reception (RX) were not
identical.
Click this link to see the size of the KW-26
in comparison to the contemporary KW-7.
The much smaller KW-7 was used for point-to-point communication in
tactical and mobile environments. It was developed in the early 1960s for NATO's TROL contest. Unlike the KW-26 it does not feature Trafic Flow Security (TFS).
Furthermore, its Fibonacci shift registered are not made with BIMAG cores,
but with
building blocks containing semiconductors (transistors).
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Complete setup
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The image on the right shows a US Navy communications centre, with a
large number of KW-26 units. The operator stands in front of seven
19" racks with two KW-26 units each: one for reception (top) and one for
transmission (bottom). At least one more rack is visible at the left of
the photograph, but it is likely that there were more.
The photograph is extracted from a booklet about the KW-26 by Melvill Klein
and issued by the NSA's Center for Cryptologic History (CCH).
➤ Read the booklet
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Electronic module
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The image on the right shows an E-AAL plug-in module from a KW-26.
It holds two CRC-6197 valves, several passive parts and 2
pulse transformers. Each KW-26 hed 10 such boards.
They providing the timing for the logic
circuits; most likely a flip-flop that acts as a ÷2 divider.
The pulse transformers have a manufacturing date code 66/43 (1966, week 43),
whilst the bottom of the board is stamped with a Moisture Fungus/Proof stamp
(MFP) of November 1966.
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MFP is a conformal coating that protects the components against moisture and
other environmental influences. It is likely that this board was released
in late 1966 or early 1967.
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The table below shows the location of the various modules of the KW-26.
Note that there are 10 identical boards marked E-AAL. These are part
of the clock train and are marked in the table below in red. Each board
divides the clock signal (E-ABA) by 2. All other boards are different.
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| Assy | Slot | ID | Rev. | Description |
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| A1 | J3 | E-AAN | |
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| A2 | J4 | E-AAR | I | |
| A3 | J5 | E-AAS | II | |
| A4 | J6 | E-ABG | |
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| A5 | J7 | E-ABF | VII | |
| A6 | J8 | E-ABE | |
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| A7 | - | - | | AUX panel |
| A8 | J11 | E-AAL | | ÷2 divider |
| A9 | J11 | E-AAL | | ÷2 divider |
| A10 | J12 | E-AAL | | ÷2 divider |
| A11 | J13 | E-AAL | | ÷2 divider |
| A12 | J14 | E-AAL | | ÷2 divider |
| A13 | J15 | E-AAL | | ÷2 divider |
| A14 | J16 | E-AAL | | ÷2 divider |
| A15 | J17 | E-AAL | | ÷2 divider |
| A16 | J18 | E-AAL | | ÷2 divider |
| A17 | J19 | E-AAL | | ÷2 divider |
| A18 | J20 | E-AAX | |
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| A19 | J21 | E-ABB | |
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| A20 | J22 | E-AAF | |
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| A21 | J23 | E-AAZ | |
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| A22 | J24 | E-ABA | | Master oscillator |
| A23 | J9 | E-ABC | | 1 |
| A24 | J9 | E-ABD | IX | 1 |
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Modules A23 and A24 are mutually exclusive.
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Device Bulk encryption device Purpose Secure long-distance point-to-point teleprinter communication Principe Electronic shift registers with valves (tubes) Model KW-26 Country USA Designator TSEC/KW-26 Manufacturer Burroughs Country USA Development 1952-1957 Production 1957 Developer NSA, Burroughs Client NSA, TCOM Users see below Predecessor 5-UCO Successor KG-84 Algorithm Based on Fibonacci shift registers using BIMAG Valves (tubes) 50 ~ BIMAG cores 800
Clock rate < 5 kHz Power 1 kW Options HW-8 Dimensions 637 × 432 × 597 mm Weight ? Quantity 15,500+
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Device Transmission Delay Compensator Purpose Compensate transmission anomalies with 21-bit delay Model HW-8 Designator TSEC/HW-8 Manufactuer ? User US Navy Quantity 450 ~
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- CRITICOMM
- US Navy
- US Army
- US Air Force
- DCA
- State Department
- CIA
- NATO
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- KWP-26C/TSEC
- KWR-26C/TSEC
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© Crypto Museum. Created: Thursday 01 September 2016. Last changed: Wednesday, 19 August 2026 - 15:14 CET.
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![Single KW-26 unit. Image extracted from photograph on CIA website [5].](img/kw26_cia_full.jpg)
![US Navy installation with 14 KW-26 units (7 for reception and 7 for transmission). Image extracted from NSA/CCH booklet about KW-26 [3].](img/kw26_nsa_large.jpg)
![Single KW-26 unit. Image extracted from photograph on CIA website [5].](img/kw26_cia_thumb.jpg "image # kw26_cia_full.jpg")
![US Navy installation with 14 KW-26 units (7 for reception and 7 for transmission). Image extracted from NSA/CCH booklet about KW-26 [3].](img/kw26_nsa_thumb.jpg "image # kw26_nsa_large.jpg")
