Zebra is a cipher from the GDR that converts letters into numbers using a special table, allowing messages to be transmitted more securely.

How did Zebra originate?

The Zebra system was developed in the GDR. The military and secret police used this system for secret messages. This occurred during the Cold War era, up until the year 1964.

After 1964, they stopped using Zebra. A new system called Kobra was introduced. The new table was named Tapir. This new system worked in the same way but offered better security.

What is Zebra?

Zebra is an encoding method that works in two steps. First, plain text is converted into a series of numbers. Then, this series of numbers is encrypted a second time using a secret key. Only someone who has the correct table and the correct key can read the message again.

Step 1: Converting letters to numbers

For the first step, a special table is used. This table has a top row and two additional rows below it. The top row contains frequently used letters. These letters are assigned a single digit. The two lower rows contain the remaining letters and punctuation marks. These are assigned two digits: one digit for the row and one digit for the column. This table format is also known as a straddling checkerboard.

Numbers are represented by repeating the same digit three times. For example, 5 becomes 555.

	0	1	2	3	4	5	6	7	8	9
	A	E	I	N
4	Ä	AU	B	BE	C	CH	D	DE	DER	ER
5	F	G	GE	H	J	K	L	M	O	Ö
6	P	Q	R	RE	S	SCH	SE	ST	SU	T
7	TE	U	Ü	UNG	V		W	X	Y	Z
8	.	:	,	–	/	(	spatie	)	“	89 (wissel)

As an example, we use the text GCWIZARD.

• The G is in row 5, column 1. G gets the value 51.
• The C is in row 4, column 4. C gets the value 44.
• The W is in row 7, column 6. W gets the value 76.
• The I is in column 2 of the top row. This row only uses column numbers. I gets the value 2.
• The Z is in row 7, column 9. Z gets the value 79.
• The A is in column 0 of the top row. This row only uses column numbers. A gets the value 0.
• The R is in row 6, column 2. R gets the value 62.
• The D is in row 4, column 6. D gets the value 46.

GCWIZARD becomes the number sequence 51447 62790 6246.

Step 2: Encrypting the numbers with a key

To provide even better security for the message, a one-time secret key is also used. This is called a One Time Pad.

In this example, we use the key 01234 56789.

The digits of the message and the digits of the key are written underneath each other. Then, the digits are added together column by column.

If the sum is ten or higher, only the last digit is written down. The tens digit is ignored.

5	1	4	4	7	6	2	7	9	0	6	2	4	6
0	1	2	3	4	5	6	7	8	9
5	2	6	7	1	1	8	4	7	9	6	2	4	6

Each code is divided into groups of 5 digits. If the last group has fewer than 5 digits, it is padded with the digit 8 or 86. GCWIZARD then becomes 52671 18479 62468.

The Zebra function

In GC Wizard, you can find this function in the folder Encoding and Codes → Zebra.

How does the function work?

The Zebra function encodes and decodes texts according to the Zebra method.