The KL-4 was a cryptodevice designed to facilitate the encryption and decryption of 4-character call signs/address groups, when PENELOPE cryptosystems were employed. The device was capable of two different methods of operation, both of which provided an output compatible with that of the KA-2 (CSP 1750), KA-3 (CSP 1756), and the KL-8. The normal method required keying material produced in a special format; the alternate method permitted use of the key lists produced for use with the KA-2, KA-3, and KL-8 devices.

The KL-4 was authorized for use with PENELOPE keying material for the encryption and decryption of 4-character call signs, address groups, and operating signal groups. The machine and unkeyed drums were unclassified. When it was keyed the result was considered to be classified "CONFIDENTIAL CRYPTO". In addition, the KL-4 was not registered but it bore a number on the name plate which could be used for local accounting. Formal authorization for access to CONFIDENTIAL cryptomaterial was required for personnel to have access to the key lists used with the KL-4. PENELOPE key lists were classified CONFIDENTIAL and were registered.

Destruction of Used Keying Material - Used key strips were to be returned to the cryptocustodian after removal from the KL-4 drums. Individual key cards were accounted for locally until destroyed. Used key strips were destroyed within 5 days after normal supersession. The complete publication, KAL-9/TSEC, including unused pages, had to be destroyed in accordance with paragraph 2 of its Letter of Promulgation.

SPECIFICATIONS AND CONTROLS

The KL-4 is a desk-top, manually operated device of the following dimensions: length, 14 inches; Width, 11 inches; Thickness, with stand, 4.5 inches.

Input Knobs - Four knobs attached to the left side of the machine control the alignment of the input drums. (See fig 1, #1)

Input Drums - Four cylindrical drums (2.875 inches wide and 7.75 inches in circumference) are located on the left side of the equipment beneath the face cover. The input key strips for the cryptoperiod are displayed on these drums. (See fig 1, #2)

Addition Rotors - Sixteen 37-character rotors, placed in four rows and four columns, are located in the center portion of the equipment. Each row is manipulated by an addition rotor setting knob on the right of the equipment, which performs an addition function. (See - fig 1, #3)

Output Drums - Four cylindrical drums (1.5 inches wide and 7.75 inches in circumference) are located on the right side of the equipment beneath the face cover. The output key strips for the cryptoperiod are displayed on these drums. (See fig 1, #4)

Addition Rotor Setting Knobs - Four knobs on the right side of the equipment are turned to move the addition rotors. (See fig. 1, # 5) Set-Up Blocking Bar - This button is located on the right side and at the bottom of the equipment. It must be depressed and held to allow the operator to push any of the column set-up levers. (See fig. # 1 ;on side of machine, lower right hand corner)