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Questions tagged [decryption-oracle]

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2
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1answer
44 views

RSA engine with inaccessible private keys - susceptible to any attacks?

We are going to integrate some hardware accelerator for RSA into our next system on chip. This chip can accelerate the core RSA operation, i.e. modular exponentiation $y=A^x \mod(N)$. The private key (...
2
votes
0answers
116 views

RSA most significant bit oracle attack

I have been reading up on RSA attacks and came across a problem that could be called a most-significant-bit (MSB) oracle attack. For the sake of clarity, let's define RSA primes $(p, q)$, private key ...
1
vote
2answers
105 views

Who calculates the private exponent $d$ in RSA?

Who calculates the private exponent $d$ in RSA? Only $(n, e)$ are public and to calculate $d$ (with $d$ being the multiplicative inverse of $e$ with respect to $\phi(n)$), the receiver need $\phi(n)$. ...
0
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0answers
132 views

Cracking stream cipher with IV

I have few ciphertexts that I want to crack. All I know is that every message is encrypted with initial vector (I don't know the length) and every message was also encrypted with the same key. I found ...
0
votes
1answer
190 views

Can Java Decrypt a 4-byte MIC? [closed]

I am using AES/CCM/NoPadding in Java, and it produces a 8-byte MAC when encrypting data. However, the data I receive, produced by a Bluetooth module, produces a 4-byte MIC. Both the Bluetooth module ...
0
votes
2answers
549 views

Recover key given partial key, IV and cipher text using CBC mode

Given a known IV and a small part of the key (not enough to use brute force) is there are any way to break CBC encryption with only one cipher text?
0
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0answers
315 views

Equivalence of two definitions of CPA security for public key cryptosystems

Definition 1: The oracle takes as input a security parameter $k$, generates a key pair $(p_k, s_k)$, and gives the public key $p_k$ to the adversary $A$. The adversary chooses two plaintexts $m_0$, $...
1
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0answers
56 views

From where I should start to study cryptography? [closed]

I am preparing for an exam which include cryptography challenges. I got five months to study. But I don't know from where I should start to study cryptography. Please help me. If possible, please ...
1
vote
2answers
807 views

Decrypt RSA ciphertext with two middle bits leak

Given RSA public key (e.g. 1024 bits) and decryption oracle that outputs 2 middle bits of decrypted ciphertext (pow(ciphertext,d,n) >> (1024/2)) & 3, how ...
4
votes
1answer
491 views

NTRU Backdoor and New Hope TLS Protocol

The pre-print, Unstructured Inversions of New Hope was posted yesterday and uses a backdoor method against NTRU to claim that Grover's algorithm and an inversion oracle could be applied to New Hope. ...
0
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0answers
46 views

Decryption Queries and its meaning in identity-based encryption

In identity-based encryption, for security proof, they sometimes describe random oracle for decryption queries. Therefore, I wonder decryption is handled by decryption oracle for all users? Users need ...
0
votes
1answer
640 views

How to decrypt an RSA ciphertext given an oracle providing the lower 8 bits of decryptions?

I have access to an oracle that can encrypt and partially decrypt a number with RSA-1024 algorithm. For encryption: \begin{equation} C = M^e\bmod n \end{equation} But for decryption, result will ...
1
vote
1answer
196 views

have a question in the book “introduction to modern cryptography”

"introduction to modern cryptography. 2ed" in page 254 "By obtaining sufficiently many estimates and letting $x_{i}$ be the majority value, $A{'}$can ensure that $x_{i}$ is equal to $gl(x, e^{i})$ ...
5
votes
3answers
2k views

Is One Time Pad considered Chosen-Plaintext Attack Secure?

If we're considering Chosen-Plaintext Attack setting, then the adversary has access to the Encryption Oracle right, and we know that OTP is only considered secure if we use the key only once. How ...
4
votes
1answer
1k views

Definition of the Decryption oracle

In the context of public-key encryption, what would be a formal definition of the decryption oracle? I know the informal definition (i.e., a function that is available to the adversary and that ...
2
votes
1answer
116 views

Encrypting decryption key

What's that property called when a scheme is secure even if you encrypt the decryption key? Some schemes have problems when your plaintext is the decryption key (or just the key if symmetric).
6
votes
1answer
460 views

Attacking a hardware AES implementation if it leaks the intermediate round states

Let's say that we have a hardware AES implementation that, on request, will encrypt or decrypt a 16-byte block of data in ECB mode using a fixed key, but refuses to reveal its fixed key. In other ...
16
votes
2answers
5k views

RSA least significant bit oracle attack

I have been reading up on RSA attacks and came across one that could be called a least-significant-bit (LSB) oracle attack. For the sake of clarity lets define RSA primes $(p, q)$, private key $d$ ...
3
votes
1answer
149 views

Could use an explanation of the notation for an oracle adversary

In the definition below, what exactly does it mean for the adversary (not even sure that's the correct term?) to equal one? $$ \underset{K}{Pr} \left [A^{F_k(\cdot)} = 1 \right ] $$ Source (Page 22/...
1
vote
2answers
171 views

What is an easy method of proving that a cryptographic oracle attack is possible?

Lets say an application is using CBC mode without authentication. The application is generating cipher text. This cipher text can be manipulated by the attacker and then transmitted back to the ...