Basic Crypto Primitives - I

[@yashjakhotiya5808]

At 24:21 it is mentioned that the total message size becomes an integer multiple of 448, but it doesn't right? total message size - 448 becomes an integer multiple of 512

[@diwakaryadav9047]

yes

[@anujkapoor04]

Request you to please help elaborate on the Algo Preprocessing and padding function using an example

[@lovekesh88]

Since K_a is public key of Alice, Bob should be able to generate a new hash value with a new message since public key is accessible to anyone.

[@yashjakhotiya5808]

Exactly. This is a substandard explanation. In public key cryptography, there are public and private keys. In this case, Alice can encrypt her message with her private key and send that digest along with the message. Everyone else can decrypt the digest with Alice's public key to check if the message sent and the decryption match. Now, if Bob alters the message, he has to alter the hash as well. But Bob cannot alter the hash as he does not have Alice's private key.

[@ishansrt]

@@yashjakhotiya5808 well what if he changes the message and changes the hash value with lets say his own key. how can Jane know whether the message is not sent by Alice or is tampered by Bob??

[@yashjakhotiya5808]

@@ishansrt Because when Jane tries to decrypt the hash with Alice's Public key, it won't match with the digest as the hash was formed from Bob's private key

[@rajvishah1877]

Very useful❤

[@cpr3296]

The size of the digest need not to be less than the size of the original message right. let us consider a message "Hie" this is less than the size of 256 bit digest. Right??

[@aayushtheapple]

Nice 💇‍♂! 😁

[@oliviafrancis7179]

Basically , the third point in SHA256 slide says that (l+1+k)%512 must be equal to 448

[@kurianify]

Is l + 1 + k = 448 mod 512 or is 448 the 'modulo' of (l + 1 + k) mod 512? Please clarify.

[@oliviafrancis7179]

Its not an equal sign in the slides its an equivalent sign. It's a way to write this: 👇 Basically , the third point says that (l+1+k)%512 must be equal to 448

[@lorikvlog]

Only few people study this course

[@AbhishekPandey-xy4uh]

In the name of IIT's, they're just wasting government resources and student's time. I thought these lecture may be very useful, but it's boring, having lots of mistakes and useless, and still, we are forced to study through these lectures, in fact, others are teaching so interestingly and also not claiming that they are very premier institute. #Paisa_Barbad

[@commenterdek3241]

Exactly man. Indians' obsession with tags and names need to end. I don't know what makes people study from these boring NPTEL lectures other than just the name of IITs. I'm from VIT Vellore, and trust me, most of our professors teach better than this lecturer.

[@adityasomani4047]

What exactly is hash??

[@divyamverma3668]

hash is an encrypted code that links two blocks.

[@oliviafrancis7179]

Output of hash function