Linked Questions

17
votes
2answers
12k views

Using the same RSA keypair to sign and encrypt

The RSA signature operation is basically the same as encrypting with the private key. In particular, both operations use the same kind of keys. Is it safe to use the same RSA keypair both for ...
9
votes
2answers
2k views

How does PKCS 1.5 solve the insecureness of Textbook RSA?

As we know, Textbook RSA is not enough safe to use because of the following issues; Guessable plaintext problem Small $e$ issue I want to know how PKCS 1.5 solved these problems.
7
votes
3answers
2k views

Finding flaw in cryptographic protocol

If you find a flaw or bug for example in Linux kernel you can create an issue in GitHub, or if you can solve it you can contribute. How about Finding a flaw in cryptographic protocol?! How can you ...
6
votes
1answer
2k views

How can I securely encrypt the same message multiple times?

I want to encrypt the same message multiple times. I want to store the encrypted messages together. I've heard if you do this with RSA, an attacker could decrypt the message with the Chinese Remainder ...
6
votes
2answers
7k views

How to verify the integrity of RSA encrypted messages?

I need to encrypt messages using PublicKeyCrypto and send it to the server, where the message should be decrypted. I'm aware of the Padding Oracle Attack and want to apply a server side integrity ...
2
votes
1answer
4k views

What's the point of OAEP?

I can't seem to wrap my head around what benefit OAEP provides (specifically with RSA). Lets consider really small numbers for a moment. If the random source in the padding algorithm gave a random ...
3
votes
3answers
2k views

How can a system be non-deterministic?

Newbie here, so forgive me if this is a stupid question. In math class we learned about RSA encryption (as a practical application of what we learned about the Euler phi function and Fermats little ...
14
votes
1answer
3k views

Bleichenbacher 1998 “Million message attack” on RSA

I have been reading Bleichenbacher's 1998 paper on a forged message attack on RSA. The paper assumes access to an Oracle that takes a ciphertext $c$ and will check the decrypted text for valid PKCS #1 ...
4
votes
1answer
2k views

Do I need to use a MAC with asymmetric encryption?

The internet has drilled into me that when I delivery any symmetrically encrypted data, I should also deliver a MAC to authenticate it before any decryption occurs. Do I also need to do this if I use ...
2
votes
2answers
900 views

Why is this a fix to Bleichenbacher's attack?

Looking at this excellent explaination of the attack, I have one additional question: It says that: ""To prevent this attack, SSL servers do not inform the client about padding woes. If decryption ...
5
votes
2answers
572 views

Timing attacks against RSA, DH and AES

I have been reading about “Timing Attacks on RSA: Revealing Your Secrets through the Fourth Dimension” by Wing H. Wong. I was wondering if this attack is feasible while signing with RSA and, if yes, ...
1
vote
1answer
2k views

Strength of RSA with OAEP

In our current system we use an encryption solution based on RSA with OAEP padding. Key size is optional but default 2048. What is the general strength of RSA with OAEP? Are there know attacks that ...
3
votes
2answers
205 views

Is this toy RSA demonstration flawed?

I want to present the basics of how RSA works to an audience of beginners in cryptography. The problem is that I am lightyears from being an expert. After reading about how RSA works in wikipedia, ...
4
votes
1answer
979 views

Is RSA vulnerable to the padding oracle attack?

I know that AES in combination with CBC mode is vulnerable against the Padding Oracle Attack. RSA also uses some kind of padding, hence can this attack be apply to RSA encrypted messages too?
1
vote
1answer
435 views

Can RSA with padding detect all errors in ciphertext?

I'm new in cryptography and there are a couple of things that i'm not sure if i understand correctly. First, when using padding (PKCS or OAEP), if the chiphertext has errors in transmission we'll we ...
2
votes
1answer
414 views

AEAD: Is it secure to decrypt the content encryption key before verifying the MAC?

The JSON Web Encryption (JWE) standard defines a number of encryption modes with the same basic form: First, the a unique content encryption key (CEK) is generated and used to encrypt the payload ...
0
votes
2answers
501 views

Is ssl_sign safe as it is using OPENSSL_PKCS1_PADDING

I've been hearing a lot of scare talk about PKCS1 padding attacks. Is PKCS1 v1.5 safe in signatures as it is practically transporting only message digest? I'm using it in one of my applications so i'...
3
votes
1answer
329 views

How to make PKCS conformation oracle for trying Bleichenbacher’s RSA attack?

I was trying to understand Bleichenbacher’s CCA attack and thought of work it out in python. Can some one throw some light on the the logic behind the oracle used to check PKCS conformation? Will a ...
3
votes
1answer
407 views

Which algorithm to use for S/MIME

I'm wondering if the algorithm 1.2.840.113549.1.1.1 (rsaEncryption) is still secure to use for S/MIME encryption. I'm afraid that the scheme is vulnerable against ...
0
votes
1answer
139 views

CCA on PKCS#5 using error feedback

My question is about attacking PKCS#5 with CCA using the error feedback. What we learnt in class about PKCS#5: CBC requires padding to whole block boundary PKCS#5: standard padding If last ...