Secure Client-Robot Messaging | Dataford Interview Questions

Build an encryption and decryption protocol to secure messages sent between a client and a robotic controller for Medra.

Implement secure_message(mode, data, key, nonce=None). Encryption must return nonce_hex:ciphertext_hex:tag_hex; decryption must validate the tag and return the original UTF-8 message or None for invalid input or tampering. The supplied compatibility vectors are normative, and the implementation must support arbitrary UTF-8 strings, keys, and nonces.

Constraints

mode is either "encrypt" or "decrypt"
data, key, and nonce contain strings
key must be nonempty
nonce must be nonempty for encryption
Input strings may contain arbitrary valid UTF-8 characters
The tag is represented by exactly two hexadecimal characters

Function Signature

def secure_message(mode, data, key, nonce=None):

Your question is Secure Client-Robot Messaging. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Build an encryption and decryption protocol to secure messages sent between a client and a robotic controller for Medra.

Constraints

mode is either "encrypt" or "decrypt"
data, key, and nonce contain strings
key must be nonempty
nonce must be nonempty for encryption
Input strings may contain arbitrary valid UTF-8 characters
The tag is represented by exactly two hexadecimal characters

Function Signature

def secure_message(mode, data, key, nonce=None):

Your question is Secure Client-Robot Messaging. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.