Pattern Recognitionand Applications Lab

Universityof Cagliari, Italy

Department of Electrical and Electronic

Engineering

CRYPTOLab

Giorgio Giacinto

giacinto@unica.it

Spring Semester 2019-2020

http://pralab.diee.unica.it

TeamsSome contents will be distributed through Teams

https://bit.ly/CTRM20

2

http://pralab.diee.unica.it

Cryptiihttps://cryptii.com

TASK #1

Given an arbitrary text of your choice, produce ciphertexts according to the Caesar cipher

Discuss the effect of different values of the shift on confusion and diffusion

3

http://pralab.diee.unica.it

Cryptiihttps://cryptii.com

TASK #2

Analyse this cyphertext and figure out the original plaintextYcqwydu jxuhu'i de xuqludYj'i uqio yv oek jhoDe xubb rubem kiQrelu ki edbo iaoYcqwydu qbb jxu fuefbuBylydw veh jetqoTry to figure out a strategy to quickly decode it

4

http://pralab.diee.unica.it

Cryptiihttps://cryptii.com

TASK #3

Analyse this cyphertext and figure out the original plaintext

ROVVY SC DROBO KXILYNI SX DROBOTECD XYN SP IYE MKX ROBO WOSC DROBO KXIYXO KD RYWO

Try to figure out a strategy to quickly decode it

5

http://pralab.diee.unica.it

Cryptiihttps://cryptii.com

TASK #4

Given an arbitrary text of your choice, produce the ciphertext according to the Vigenere cipher

See the effects on slightly changing the original text by keeping the key unchanged

See the effects of the length of the key

See the effects of small changes in the key (fixed length)

6

http://pralab.diee.unica.it

Cryptiihttps://cryptii.com

TASK #5

Given the following cyphertext, find the corresponding plaintext by identifying the encryption algorithm and the key, if any

Rahttrr gvras'z az lrnjrw

Wa'f pefl ws hcb gcc

Ab vruz irwsj hg

Nkccr fw bazl byf

Vxetvbr jzs gsi crccus

Svgmat tba hvqlc

7

http://pralab.diee.unica.it

Cryptiihttps://cryptii.com

TASK #6

Given an arbitrary text of your choice, produce digests using MD5, SHA-2

See the effects on slightly changing the original text

How easy is it to have collisions?

8

http://pralab.diee.unica.it

Cryptiihttps://cryptii.com

TASK #7Given an arbitrary text of your choice, produce the ciphertext according to the AES cipherWhat are the effects on slightly changing the original text by keeping the key unchanged?What are the effects of the length of the key on the resulting text?What are the effects of small changes in the key (fixed length)?

9

http://pralab.diee.unica.it

Cryptool 2https://www.cryptool.org/en/cryptool2

TASK #8

Cryptoanalysis

Try using the tool to decrypt a ciphertext that was encrypted using the Caesar cipher. Try different texts, different shifts

Please comment about the difficulty of automatic decryption

10

http://pralab.diee.unica.it

Cryptool 2https://www.cryptool.org/en/cryptool2

TASK #9

Cryptoanalysis

Try using the tool to decrypt a ciphertext that was encrypted using the Vigenere cipher. Try different texts, different keys

Please comment about the difficulty of automatic decryption

11

http://pralab.diee.unica.it

Cryptool 2https://www.cryptool.org/en/cryptool2

TASK #10

Generate RSA keys, encrypt a decrypt a text

12

http://pralab.diee.unica.it

Cryptool 2https://www.cryptool.org/en/cryptool2

TASK #11

Simulate the Diffie-Hellman key exchange

13

http://pralab.diee.unica.it

Cryptool 2https://www.cryptool.org/en/cryptool2

TASK #12

Experiment with different random number generators

14

http://pralab.diee.unica.it

Cryptool 2https://www.cryptool.org/en/cryptool2

TASK #13

Use Cryptool to implement the digital signature of a plaintext

15

http://pralab.diee.unica.it

Cryptool 2Digital Signature of a plaintext

16