The Code Machine
by Kenneth Hart
from Micro Update #1 (February 1983)


Keep your secrets safe

Can you keep a secret? Youngsters with 16K ZX81s will enjoy passing
confidential messages with my program. It garbles text into virtually
unbreakable code, based on ciphering carried out by the armed forces.

Text is converted into blocks of five encoded characters using the
ZX81's random numbering. If the message does[n't] equal a multiple of
five the program packs it with spaces. I reckon it's foolproof for any
youngster to use.

The program is fairly self-explanatory. You are asked first, in line
30, whether you want to encode or decode and then, at line 70, for a
code number from 1 to 65535. Without this number the recipient cannot
decode the message.

Your message is checked for length and then printed in encoded format,
with a copy (starting at line 2000) if you wish. The decoding routine
begins at line 1000.

