Tagged Questions
2
votes
1answer
60 views
How does OAEP improve the security of RSA?
The heart of OAEP algorithm used for RSA encryption are the cryptographic hash functions $H$ and $G$.
Does everybody (so also an adversary) know these functions?
If YES: How does it help the ...
2
votes
2answers
127 views
Chain several RSA encryptions without increasing the message size
I would like to be able to encrypt the output of RSA with RSA again without having the output grow in size over time.
In other words, I have some data $D_0$ which I want to encrypt with RSA: $D_1 = ...
1
vote
2answers
100 views
Is semantic security important in a hybrid cryptosystem?
RSA doesn't provide semantic security when used unmodified, and neither does the commonly used PKCS#1 v.1.5 padding scheme for encryption.
Is this a problem for hybrid cryptosystems at all?
My ...
3
votes
2answers
180 views
RSA blind signatures in practice
Hi I have a problem with moving my blind signature implementation from educational (textbook RSA) to more practical (padded RSA) side.
David Chaums paper gives a following figure:
$r$ - blinding ...
4
votes
1answer
122 views
Why does OAEP have 2 rounds with 2 random oracles?
I strive into understanding why OAEP has two rounds of computations and not just one. I.e: Wouldn't it be safe to hash the random number r and XOR it with the original message?What security risks if ...
2
votes
4answers
841 views
Why is padding used for RSA encryption given that it is not a block cipher?
In AES we use some padded bytes at end of message to fit 128/256
byte blocks. But as RSA is not a block cipher why is padding used?
Can the message size be any byte length (is the encrypting agent
...
5
votes
3answers
426 views
Is RSA padding needed for single recipient, one-time, unique random message?
I want a way to encrypt files using this process: http://crypto.stackexchange.com/a/15 . That is: generate a random password, use that to AES-encrypt a file, and use an RSA public key to encrypt the ...
5
votes
1answer
355 views
RSA-OAEP Input Parameters
When creating padding for RSA using OAEP, a message is prepared as follows:
Hash(Input Parameter) || Zeros || 1 || Message
My question is, what should the Input ...
6
votes
2answers
268 views
What is the key strength reduction encrypting only 160 bits of data using RSA1024 for signatures
I am attempting to determine the strength of an incorrectly implemented 1024 bit RSA signature scheme. The weakness in the implementation is that the padding data lacks random numbers. As a result, ...
4
votes
2answers
295 views
Does RSA padding have to be unpredictable if the payload is?
I'm trying to understand the precise requirements on padding when using RSA for encryption.
Suppose Alice uses RSA to encrypt a payload $M$ that cannot be guessed (say, a random nonce): Alice send ...
2
votes
1answer
408 views
Is RSA of a random nonce with no padding safe?
Consider the following protocol: Bob has a private RSA key $B_{priv}$, and Alice knows the public key $B_{pub}$. Alice wants to send confidential messages to Bob (no integrity intended). To send a ...
