Questions tagged [decryption-oracle]

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21 questions
16 views

Do AEAD algorithms and encrypt-then-MAC mitigate external decryption oracles?

I'm curious about a possible attack scenario that I'm not sure exists. If it is possible, I'd like to know if and how AEAD algorithms and encrypt-then-MAC implementations protect against it. The ...
25 views

Does the oracle have to have access to the encryption key to the padding oracle attack to work (CBC & PKCS#7)?

Does the oracle have to have access to the encryption key to the padding oracle attack to work (CBC & PKCS#7)? I tried much to get a attach to work, but the oracle doesn't have access to the ...
167 views

Help understanding how to decrypt cipher

I am trying to create a padding oracle attack to decrypt a cipher that is encrypted with cbc and PKCS#7 padding. My first step is just to try and decrypt the second block. I have read a lot about it,...
55 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 (...
216 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 ...
117 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 $\phi(n)$. ...
265 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 ...
604 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?
61 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 ...
921 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 ...
532 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. ...
50 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 ...
793 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 ...
220 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 $gl(x, e^{i})$ ...
3k 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 ...
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 ...
120 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).
496 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 ...
6k 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 $d$ ...
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/...