Digital signatures in Cybersecurity - Step-by-Step Execution

Concept Flow - Digital signatures

Message to send

↓

Hash the message

↓

Encrypt hash with sender's private key

↓

Send message + encrypted hash (digital signature)

↓

Receiver gets message + signature

↓

Receiver hashes received message

↓

Receiver decrypts signature with sender's public key

↓

Compare decrypted hash with receiver's hash

↓

Message is authentic and unchanged

No↓

Message is altered or sender is fake

The sender creates a hash of the message and encrypts it with their private key to form a digital signature. The receiver decrypts the signature with the sender's public key and compares it to their own hash of the message to verify authenticity.

Execution Sample

Cybersecurity

message = "Hello"
hash_msg = hash(message)
signature = encrypt(hash_msg, private_key)
send(message, signature)
received_message = receive()
received_hash = hash(received_message)
decrypted_hash = decrypt(signature, public_key)
verify = (received_hash == decrypted_hash)

This code shows how a message is signed by hashing and encrypting the hash, then verified by decrypting and comparing hashes.

Analysis Table

Step	Action	Value/Result	Explanation
1	Hash the message	hash_msg = hash("Hello")	Creates a fixed-size hash from the message
2	Encrypt hash with private key	signature = encrypt(hash_msg, private_key)	Encrypts hash to create digital signature
3	Send message and signature	message + signature sent	Both message and signature are sent to receiver
4	Receiver hashes message	received_hash = hash("Hello")	Receiver creates hash from received message
5	Receiver decrypts signature	decrypted_hash = decrypt(signature, public_key)	Decrypts signature to get original hash
6	Compare hashes	received_hash == decrypted_hash	Checks if message is authentic and unchanged
7	Result	True	Hashes match, message is verified

💡 Hashes match, so the message is authentic and unchanged

State Tracker

Variable	Start	After Step 1	After Step 2	After Step 4	After Step 5	Final
message	"Hello"	"Hello"	"Hello"	"Hello"	"Hello"	"Hello"
hash_msg	undefined	hash("Hello")	hash("Hello")	hash("Hello")	hash("Hello")	hash("Hello")
signature	undefined	undefined	encrypt(hash_msg, private_key)	encrypt(hash_msg, private_key)	encrypt(hash_msg, private_key)	encrypt(hash_msg, private_key)
received_hash	undefined	undefined	undefined	hash("Hello")	hash("Hello")	hash("Hello")
decrypted_hash	undefined	undefined	undefined	undefined	decrypt(signature, public_key)	decrypt(signature, public_key)
verify	undefined	undefined	undefined	undefined	undefined	True

Key Insights - 3 Insights

Why do we hash the message before encrypting?

Hashing creates a fixed-size summary of the message, making encryption faster and ensuring the signature is small. See execution_table steps 1 and 2.

Why does the receiver decrypt the signature with the sender's public key?

Because the signature was encrypted with the sender's private key, decrypting with the public key verifies the sender's identity. See execution_table step 5.

What happens if the hashes do not match?

It means the message was altered or the signature is fake, so the message is not authentic. See execution_table step 6.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the purpose of encrypting the hash?

A To create a digital signature that proves the sender's identity

B To hide the entire message content

C To make the message longer

D To decrypt the message

💡 Hint

Refer to the 'Action' and 'Explanation' columns in step 2 of execution_table

At which step does the receiver verify the message authenticity?

A Step 5

B Step 6

C Step 3

D Step 1

💡 Hint

Check the 'Compare hashes' action in execution_table

If the message changes during transmission, what will be the value of 'verify' at the final step?

A True

B Undefined

C False

D Encrypted

💡 Hint

Look at variable_tracker for 'verify' and the explanation in key_moments about hash mismatch

Concept Snapshot

Digital signatures use a hash of the message encrypted with the sender's private key.
The receiver decrypts the signature with the sender's public key and compares hashes.
Matching hashes prove the message is authentic and unchanged.
This process ensures integrity and sender identity.
It is widely used in secure communications.

Full Transcript

Digital signatures work by creating a hash of the message, which is a short fixed-size summary. This hash is then encrypted using the sender's private key, forming the digital signature. The sender sends both the original message and this signature to the receiver. The receiver hashes the received message again and decrypts the signature using the sender's public key. If the decrypted hash matches the receiver's hash, the message is confirmed to be authentic and unchanged. If not, it means the message was altered or the signature is fake. This method ensures both the integrity of the message and the identity of the sender.