Introduction to Cryptography

• You have received the following encrypted message:

“Xjnvw lc sluxjmw jsqm wjpmcqbg jg wqcxqmnvw; xjzjmmjd lc wjpm sluxjmw jsqm bqccqm zqy.” Zlwvzjxj Zpcvcol

You can guess that it is a quote. Who said it?

Miyamoto Musashi

• Decrypt the file quote01 encrypted (using AES256) with the key s!kR3T55 using gpg. What is the third word in the file?

waste

• Decrypt the file quote02 encrypted (using AES256-CBC) with the key s!kR3T55 using openssl. What is the third word in the file?

science

• Decrypt the file quote03 encrypted (using CAMELLIA256) with the key s!kR3T55 using gpg. What is the third word in the file?

understand

• On the AttackBox, you can find the directory for this task located at /root/Rooms/cryptographyintro/task03; alternatively, you can use the task file from Task 2 to work on your own machine.

Bob has received the file ciphertext_message sent to him from Alice. You can find the key you need in the same folder. What is the first word of the original plaintext?

Perception

• Take a look at Bob’s private RSA key. What is the last byte of p?

e7

• Take a look at Bob’s private RSA key. What is the last byte of q?

27

• On the AttackBox, you can find the directory for this task located at /root/Rooms/cryptographyintro/task04; alternatively, you can use the task file from Task 2 to work on your own machine.

A set of Diffie-Hellman parameters can be found in the file dhparam.pem. What is the size of the prime number in bits?

4096

• What is the prime number’s last byte (least significant byte)?

4f

• On the AttackBox, you can find the directory for this task located at /root/Rooms/cryptographyintro/task05; alternatively, you can use the task file from Task 2 to work on your own machine.

What is the SHA256 checksum of the file order.json?

2c34b68669427d15f76a1c06ab941e3e6038dacdfb9209455c87519a3ef2c660

• Open the file order.json and change the amount from 1000 to 9000. What is the new SHA256 checksum?

11faeec5edc2a2bad82ab116bbe4df0f4bc6edd96adac7150bb4e6364a238466

• Using SHA256 and the key 3RfDFz82, what is the HMAC of order.txt?

c7e4de386a09ef970300243a70a444ee2a4ca62413aeaeb7097d43d2c5fac89f

• On the AttackBox, you can find the directory for this task located at /root/Rooms/cryptographyintro/task06; alternatively, you can use the task file from Task 2 to work on your own machine.

What is the size of the public key in bits?

4096

• Till which year is this certificate valid?

2039

• You were auditing a system when you discovered that the MD5 hash of the admin password is 3fc0a7acf087f549ac2b266baf94b8b1. What is the original password?

qwerty123