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Web master's note: Unfortunately the source of this information cannot be credited because it is unknown. One manul for this product is dated 1981.

The continuing demands from the military forces for an even greater degree of security in their cryptographic systems has encouraged Marconi Space and Defence Systems to develop a system millions of times more secure than the systems currently being used. With its long-standing background and experience in providing high security digital data transmission, culminating in the MARCRYP range, the company now presents the MARCRYP Mark II series.

Marcryp II Unit

The two major advances that place MARCRYP Mark II well ahead of present cryptographic equipment have been made in the areas of Sequence Length and Key Setting.

Sequence Length

The provision of such high grade security now being demanded depends largely on the length and complexity of pulse sequences which encrypt the digitized message. The original MARCRYP provided a maximum of 17,000 million bits. The minimum provided by the MARCRYP Mark II is 1,125 million million bits. This guaranteed minimum is equivalent to more than 2,000 years continuous use of one code setting at 16 kbits/sec . This prodigious sequence length offers such an enormous degree of security that no other techniques such as "modification by message" need be incorporated, thus eliminating the possibility of error extension.

Key Setting

The original method of key setting by thumbwheel switches as used in the MARCRYP Mark I range cannot contend with the greatly increased key-variable lengths employed in the new Mark II series.

The latest MARCRYP, the Mark II uses a "Key Management Unit to arrange the key settings. This  Key Management Unit can be kept well away from sensitive areas and  in a place where it can be protected.

The key settings made in the Key Management Unit are transferred  to a small,  pocket-sized, battery operated device called a Fill Gun. The function of the Fill Gun is to transfer the unique arrangement of key settings from the  Key Management Unit to the MARCRYP encryption unit which is remote from the Key Management Unit.

There are 2¹⁴⁴ key variables available, 2¹²⁸ directly from the Gun and 2¹⁶ from the thumbwheel  switches on each cryptographic equipment.  It can vary the sequence loaded by the Fill Gun and provide extra key management flexibility called for on occassion  in modern tactical warfare.

Of the 128 bits from the Manageme