Question

Consider each situation in turn and for each say whether hashing, encryption or both would be applicable, and briefly outline how it would be used.

1. A user logs in to an online shop.
2. A user shares a document with another person over a network. The document is not confidential, but the parties involved want to be able to check the document has not been accidentally corrupted on route.
3. A user shares a document with another person over a network and wants to be able to 'sign' it, so the recipient can be sure who the document came from

Answer 1

hashing:

• converts data of any length to a fixed length
• one-way
• helps in checking the authenticity of the data transferred

encryption:

• converts data into unreadable format
• two-way
• helps in protecting the data transferred from unintended receivers

1. A user logs in to an online shop.

• Uses encryption
• Only authenticated users are allowed to login, so they use a password which helps in identifiying them

2. A user shares a document with another person over a network. The document is not confidential, but the parties involved want to be able to check the document has not been accidentally corrupted on route.

• Uses hashing
• Hashing the document and comparing it with the hash of document sent by the sender will identify whether the document is tampered or not.  

3. A user shares a document with another person over a network and wants to be able to 'sign' it, so the recipient can be sure who the document came from

• Uses encryption and hashing
• Here the document is signed => the document is hashed. The sender encrypts the document with their private key. The receiver just have to use the public key of sender to decrypt and to check the signature
• The document is signed by hashing it and this will act as the signature
• The receiver needs to compare the received hash value with the hash of document.