Linked Questions

10 votes
3 answers
9k views

Why hash or salt when signing? [duplicate]

EDIT: Just wondering why was this question closed as a duplicate of a question asked almost 2 years after this one... I've seen an example of how to sign using RSA. Besides the signing itself (s = m^d ...
ispiro's user avatar
  • 2,025
1 vote
2 answers
2k views

Why is SHA256 used as a layer on top of Digital Signature [duplicate]

Digital Signatures use an asymmetric algorithm, meaning that if I want to apply a digital signature to a document I sign it with my own private key and send it to the recipient. The recipient, thanks ...
Tarta's user avatar
  • 129
3 votes
1 answer
3k views

Why hash function are used in digital signatures? [duplicate]

In the lectures I see, hash functions are always used when we want to sign a document $d$. My question is why they are used in digital signatures? Maybe, because it is more easy and fast to calculate ...
juaninf's user avatar
  • 2,711
1 vote
0 answers
1k views

RSA - Why should we sign hash rather than raw content? [duplicate]

Apart from obvious performance considerations, is there any mathematical or crypto reasons that imply that we sign a hash rather than a raw content ? I read that it was because the hash must fit in ...
crypto-learner's user avatar
7 votes
3 answers
3k views

Do RSA signatures really need padding?

For encryption, we want identical plain-text's to encrypt to unique ciphers, also called Semantic Security. For Signatures, the plain-text (i.e. message hash) is not a secret. The plain-text, if you ...
randyrand's user avatar
  • 173
8 votes
5 answers
2k views

Why do we need to compute message digest of a message first while signing it?

Why is it more efficient to compute a message digest (message & signature) rather than sign the message directly?
Vinnie's user avatar
  • 105
3 votes
1 answer
3k views

Why the need to hash before signing small data?

I’ve got two questions: I’m doing the following: Data : uuid + int + nonce Signature: ECDSA(sha256(Data) ) To verify the signature: ...
jaybny's user avatar
  • 203
1 vote
2 answers
3k views

How is message length involved in public/private-key encryption?

I've just read this question regarding why to sign only the hash of a message. I kind of understood the answer, but the question arisen is now: Why can I encrypt any text messages with the same ...
user2084865's user avatar
5 votes
1 answer
746 views

Why ISO/IEC 9796 (signature with message recovery) instead of just encrypt the short message with private key?

I've had a look at “Practical Cryptanalysis of ISO/IEC 9796-2 and EMV Signatures” and read the very good answer https://crypto.stackexchange.com/a/17846/59673 and I understand that signature and ...
Kzar's user avatar
  • 153
3 votes
1 answer
2k views

Understanding SSL Certificate Signing

Original thread: Why hash the message before signing it with RSA? Please correct the diagram below so I can better understand how certificates are created and signed by a third party CA: https://i....
user3253260's user avatar
0 votes
1 answer
915 views

RSA signature send signature with encrypted message?

What is the correct procedure in sending an authenticated message, I've been researching and have been getting different answers, such as hash-then-sign [1], [2] , sign-then-encrypt [3] (but the link ...
user153882's user avatar
1 vote
2 answers
121 views

Public Key Encryption for Message Confidentiality

In public-key encryption, if the decryption algorithm is $$\text{Dec}(k_i,\text{Enc}(K_i,p))=p$$ where $k_i$ = receiver's private key and $K_i$ = receiver's public key what would be the algorithm for ...
Hardrocker's user avatar