The Swedish SA-1 is an example of a cipher machine probably designed by a
cryptanalyst. It is an attachment for a five level teleprinter. In
common with the SZ42, it has two sets of five wheels which generate the
XOR additive key. However the stepping is more secure than that used in
the SZ42. The five B wheels on the right, roughly equivalent to the SZ42
'chi' wheels all step forward by one position for every character
enciphered. The A wheels on the left, equivalent to the SZ42 'psi'
wheels, all step either one or two positions, depending on the parity
of a secondary set of five switches on the B wheels. Attacks similar to
that used on the SZ42 using the intermittent stepping of the psi wheels
are therefore not possible. Each bank of five wheels has 19, 21, 23,
25 and 26 settable pins which can be moved to the left or right
according to the inner key setting.
Further details of this machine can be found on an archived copy of
Toby's Crypto page
Click Here to download The graphical simulator for this cipher machine. (48K)
(Requires Windows 3.1/95/98/NT4/2000/XP with at least 800x600 display and 16 bit color)
