ZUGZWANG (Concrete Instance)

This repository contains a reference implementation of the proof-of-concept block cipher, ZUGZWANG (concrete instance/encryption). The cipher is basically a four-round Feistel construction, but has an innate backdoor. The key is revealed through the ciphertext when the plaintext matches a backdoor entry (which is known only to the cipher designer), otherwise the cipher is secure. See this paper on ePrint for its specification and other information.

Requirement

• Python 3
• Pycryptodome

Test Cases

Case	1
Key	10000000000000000000000000000000
Backdoor Entry	10000000000000000000000000000000
Plaintext	10000000000000000000000000000000
Ciphertext	10000000000000001000000000000000
Recovered Key	10000000000000000000000000000000

Case	2
Key	10000000000000000000000000000000
Backdoor Entry	10000000000000000000000000000000
Plaintext	00000000000000000000000000000001
Ciphertext	77882970d3ee73581cce9b1ae1e66cbd

Case	3
Key	10000000000000000000000000000000
Backdoor Entry	10000000000000000000000000000000
Plaintext	f0000000000000000000000000000000
Ciphertext	d5c03bdfec4e0fcf853645f83c6d74ef

Case	4
Key	10000000000000000000000000000000
Backdoor Entry	0000000000000000000000000000000f
Plaintext	0000000000000000000000000000000f
Ciphertext	100000000000000f0000000000000000
Recovered Key	10000000000000000000000000000000

Case	5
Key	10000000000000000000000000000000
Backdoor Entry	10000000000000000000000000000000
Plaintext	0000000000000000000000000000000f
Ciphertext	81cca7e35cf90690105da7090fbb253d

Case	6
Key	f1000000000000000000000000000000
Backdoor Entry	1000000000000000000000000000000f
Plaintext	0000000000000000000000000000000f
Ciphertext	d69db61c7ef55b8d4e0b7e87b18ee158

Case	7
Key	3cf28000471a74d22d81b6c98a3dbe33
Backdoor Entry	1831bcaa5bee08e639864e4823183090
Plaintext	1831bcaa5bee08e639864e4823183090
Ciphertext	0574ce486402444235b00a63d1d3b6d5
Recovered Key	3cf28000471a74d22d81b6c98a3dbe33

Case	8
Key	3cf28000471a74d22d81b6c98a3dbe33
Backdoor Entry	1831bcaa5bee08e639864e4823183090
Plaintext	9eac455e039a58928e163658e1493a20
Ciphertext	7a7700e9f5f4f974e9ba2834160cf284
Note	This test case is currently hardcoded