Linked Questions

1 vote
0 answers
1k views

Textbook RSA Signature attacks (without message padding) [duplicate]

I have been reading as much as possible, but I haven't so far found anything exactly like what I'm looking for. I have a couple of questions (given what I know below): One, is it possible to find d? ...
Chris seigman's user avatar
16 votes
4 answers
5k views

Is there a cryptographic algorithm that can make a "lottery ticket"?

With public-key cryptography, I know Alice can "seal" a message that only Bob can open. But in that case, Alice knows the message that she is sealing. What if Alice wants to seal a random ...
mherzl's user avatar
  • 263
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
6 votes
1 answer
3k views

RSA Signature using SHA-256 is secure?

Is following RSA signature scheme secure against forgery and prevents breaking text book RSA? $$y = \operatorname{SHA-256}(m)$$ $$s = y^d\bmod N$$ where $m$ is message of arbitrary length, $y$ is the ...
crypt's user avatar
  • 2,449
5 votes
2 answers
1k views

RSA Signing - Existential forgery and message prefix question. It's a weird one

I'm new to this. Please be kind. I have a theoretical question that I would like sanity checked: Bob and Alice are doing RSA signing without a hash function -- just putting a message in, and getting a ...
Kendrick Taylor's user avatar
3 votes
2 answers
715 views

Does it make any sense to sign a GCM authentication tag with RSA?

To achieve double insurance for authentication, can we sign the GCM final tag with using RSA? with RSA, no one is able to create his own tag since the private key is not known. However, according to ...
Pi-Turn's user avatar
  • 83
6 votes
1 answer
775 views

Can RSA-PSS signing be made deterministic without loss of security?

Is it possible to make RSA-PSS signing deterministic without loss of security? Specifically, I would use Blake2b of the key and message to generate the salt.
Demi's user avatar
  • 4,793
2 votes
2 answers
275 views

Signatures from asymmetric encryption

Let $(K_{enc},K_{dec})$ be an asymmetric key-pair. It seems to me that a signature scheme can be created by letting the public verification key be $K_{ver}=K_{dec}$ (the asymmetric decryption key) ...
yoyo's user avatar
  • 420
2 votes
1 answer
2k views

Is padding of the digest needed in SHA256 with RSA-2048 scheme?

For a signing scheme involving generating a $256$ bit digest using SHA256 followed by RSA with $2048$ bit modulus, the signature would always be 256 bit without padding even though signatures of up to ...
Tabish Mir's user avatar
0 votes
3 answers
2k views

Sign MD5 hash with RSA [duplicate]

I have to hash a message with MD5, digitally sign it, and then verify. I have looked around, but I can't find a step-by-step example. I understand how RSA works when a message is given as number (not ...
jannikaan's user avatar
1 vote
2 answers
1k views

Digital signature forgery

My understanding of digital signatures is as follows: Alice hashes a message with a one-way cryptographic hash function, the output of which is called the message digest. She then encrypts the digest ...
user216096's user avatar
1 vote
1 answer
912 views

RSA security when using short messages

We know that a short message encrypted with RSA can easily be brute forced. Lets say Bob encrypts a message containing just "Hi" and encrypts it with Alice's public key. Anyone can try ...
Peter2223's user avatar
0 votes
2 answers
299 views

PKI Encrypted hash vs Signing

I have a confusion in a concept under cryptography context. What is the major difference between an encrypted hash and digital signed hash? I have used PKI Encryption i.e. public / private key based ...
user79366's user avatar
0 votes
2 answers
501 views

What does it mean if two files created by the same person shares the same SHA256 hash?

Okay so I've got an assignment for cyberlaw and this could be irrelevant to the question. But I have a situation where someone signed a a will using an advanced electronic signature, but this ...
Phillip's user avatar
1 vote
1 answer
287 views

PKCS RSA - Why do we need encoding [duplicate]

In the RSASSA-PKCS-v1_5 signature scheme, the first step is to perform an encoding on the hashed data. (0x00||0x01||PS||0x00||T). Is this encoding important for security ? What happens if the hash is ...
cmdEvo's user avatar
  • 57

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