Questions tagged [rsa]
An asymmetric (e.g. public-key) cryptosystem, based on modular exponentiation with big exponents and modulus. RSA can be used both for signature and encryption with proper paddings.
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questions with no upvoted or accepted answers
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Who first published the interest of more than two prime factors in RSA?
Multi-prime RSA is now a well known technique (described here): it uses $k>2$ distinct secret prime factors in the public RSA modulus, with the advantage that, using the CRT, we can gain a speed ...
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Fewest qubits required for the discrete logarithm problem and integer factorization
According to a paper from 2002, the most efficient circuit to factor an $n$-bit integer requires $2n+3$ qubits and $O(n^{3}\lg(n))$ elementary quantum gates, assuming ideal qubits. Later on, according ...
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Name of an archaic type of RSA padding (0BBBBBBB…)
In some legacy code, I encountered RSA signature padding in the following format (hexadecimal):
0B BB BB BB BB BB BB ... BB BB <hash>
Is there a name for ...
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477 views
RSA factorization with special primes
Suppose that primes for RSA modulus are generated using formula:
$P_i(x,y) = \operatorname{next\_prime}(x^{z_i}+y^{z_i}) = x^{z_i}+y^{z_i}+d_i$
where $x,y$ are unknown random numbers with size 128 ...
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630 views
Are there attacks against broken RSA signature pad checking with $e = 65537$?
Let's say that an RSA implementation of PKCS #1 signatures fails to validate that the 00 01 FF FF FF ... FF 00 portion of the decrypted signature is exactly as long ...
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Bleichenbacher RSA1024 signature forgery, closed-form solution
Hal Finney's writeup (Bleichenbacher's RSA signature forgery based on implementation error) shows a formula for RSA3072. I tried to replicate the attack for RSA1024 and failed, since the first term of ...
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Finding the period of a function with a single output qubit - impact on RSA
In this paper,May and Schlieper claim that one can find the period of a function $f()$ by embedding $h \circ f = h(f(x))$ for input $x$. This would have the immediate consequence of reducing the ...
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211 views
Is there an efficient way to verify the union of two RSA accumulators?
More specifically, say we have one RSA accumulator $A_{S_1}$ accumulating set $S_1$ and another RSA accumulator $A_{S_2}$ accumulating set $S_2$. Does there exist a sublinear method to securely verify ...
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91 views
Why do one-way accumulators use rigid integers as the modulus?
In the paper that introduced one-way accumulators, the author's justify their use of rigid integers as the modulus with the following:
The advantage of using a rigid integer $n = pq$ is that the ...
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77 views
Computing cost for a trillionaire to compute GNFS in RFC 3766
RFC 3766, Section 4.1 discusses picking $n$ to achieve some target cost for employing the GNFS, i.e., $T$ is known and $N$ is unknown in the below equation:
$$T = \kappa \cdot \exp{\left(c \cdot (\ln{...
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96 views
What followed findings of A. Lenstra et al. concerning shared factors of practical RSA moduli?
A. Lenstra et al. had a paper in 2012 "Ron was wrong, Whit is right", in which one reads: "What surprised us most is that many thousands of 1024-bit RSA moduli, including thousands that are contained ...
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158 views
Is MITM possible after key exchange phase done successfully in RSA?
Is MITM attack theoretically possible after public/private key pair exchange is done successfully. Say Alice and Bob have genuine public keys of each other. Is MITM possible further during ...
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1answer
107 views
RSA Accumulators with auxiliary information or known trapdoor information
In "Universal Accumulators with Efficient Nonmembership Proofs" by
Jiangtao Li1, Ninghui Li2, and Rui Xue3 section "How to compute witness with the auxiliary information" the authors write:
"The ...
3
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89 views
RSALib prime generation - derive number of primes
I'm working on factorizing a ~450 bit key that I know has been generated with RSALib and thus is vulnerable to ROCA. Now reading the original paper, I can see that the primes are generated in the ...
3
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482 views
How to determine the correct padding to use for rsa signing?
Before today I didn't know the difference between RSA padding for encryption and for signing, I think this answer describes it pretty succinctly, however, I don't know if there is an optimal padding ...
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640 views
RSASSA-PSS p1v2.1 (rfc 4056) signing
I'm signing mails with the RSASSA-PSS (p1v2.1) certificate. When I click Details, it shows "Signature Algorithm: RSASSA-PSS".
openssl x509 -text shows
...
3
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379 views
RSA - factorizing $N$ to get $p$ and $q$
I need to decrypt a message encrypted using RSA. I only know the public keys $n$ and $e$.
I need to get the private key $p$ and $q$ in order to get the decryption exponent $d$. Now to do so, I know ...
3
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169 views
IND-CCA1 RSA padding?
I've found a way to complete a task which I'd solve with passwords or by sending keys over the wire (otherwise) by using RSA's homomorphic property.
I'm restricted to RSA (any padding; for hardware ...
3
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490 views
Relations between RSA and DLOG, factoring and DLOG
Definition: (The generalized Diffie-Hellman problem)
Let $n=pq$ for two large primes $p,q$. Given $x, x^a, x^b,n$, find $x^{ab}\pmod{n}$.
(1) Is there a known reduction from the GDH problem to ...
3
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165 views
How much plainext could be known without reducting security of RSA?
It is known, for example, that exposing 50% of most significant bits of RSA private exponent does not provide security risk (when a small public exponent it used). So how to qualify security ...
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WebCrypto SubtleCrypto RSA sign/verify AND encrypt/decrypt?
I have a project where I'd like to use public-key cryptography in both typical sign/verify situations and encrypt/decrypt situations. For example, I'd like to create a self-signed X.509 certificate ...
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How to derive a 4096 bit or 8192 bit RSA private key from a (BIP39) mnemonic seed?
How to derive a 4096 bit or 8192 bit RSA private key from a (BIP39) mnemonic seed?
Any tool available for this?
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25 views
What are some examples of out of bound channels that work over the Internet in practice?
If I want to verify a public key (be it RSA, PGP, etc.) with another client over the Internet only, what are some viable out-of-bound channels for verification? Which channels have been used in ...
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63 views
Recursive RSA encryption
I have a ciphertext $C$ encrypted with public key $pub_C$, which contains ciphertext $B$ and $pub_B$, $$C= E_{pub_C}(B\mathbin\|pub_B)$$
Ciphertext $B$ is encrypted with $pub_B$ and contains $pub_A$ ...
2
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40 views
RSA: Blinding versus fixed-time computation
For RSA, what is the standard solution against timing attacks? I know about RSA blinding as one solution.
Another solution is to always compute both the squared value and square-and-multiply values, ...
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64 views
Concept for a RSA “repeater”. Is it sensible?
I have been using RSA signed/encrypted mailing a lot recently. Naturally, I wanted to use RSA mailing also on my phone, not only on my computer. However, I feel uneasy having my private key on my ...
2
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1answer
130 views
Using YubiKey to store a PIN-protected secret for disk encryption
I want to store a secret on YubiKey and use it for disk encryption. It's crucial that it be PIN protected. There are a limited number of PIN tries, and after three attempts the YubiKey would be ...
2
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117 views
What are the known attacks on $\phi$-hiding assumption? How to chose its parameters?
$\phi$-hiding assumption states the following.
Sample 2 random primes $e_0$ and $e_1$ in the range $[5, 2^{\lambda/4}]$. Sample $N = pq$ of length $\lambda$ ($p$ and $q$ are large primes of length $0....
2
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185 views
Sharing RSA private key between SSH and SSL services. How bad is it?
An appliance uses a curious way of obtaining ssh-rsa host keys: There is a single configuration option "management certificate" that sets RSA private keys both for HTTPS and SSH management.
...
2
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382 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 ...
2
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212 views
Chinese Remainder Theorem and Elgamal
I am studying an encryption scheme which is Elgamal-like where I think CRT can help optimise the encryption and decryption but I am not sure if I am applying CRT the correct way.
I have a cyclic ...
2
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0answers
27 views
What are SNFS-safe limits for an RSA moduli optimized for simple modular reduction?
I consider $n$-bit RSA moduli $N$ having high-order bits starting by with $k$ bits at 1, then $k$ bits at 0, then $m-2k$ bits at ...
2
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206 views
Where shoul I store private/public keys and how should I share it?
I'm new in terms of encryption and I have to encrypt the data between two Java Spring applications, one have serves as MVC framework and other as Web Service, I'm implementing an asymmetric encryption ...
2
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0answers
66 views
Asymmetric encryption property required in an authentication protocol
We want to choose an asymmetric encryption scheme for use as follows:
A device holds its private key, with the corresponding public key known and trusted by all.
The device also holds a small $b$-bit ...
2
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165 views
What kind of RSA padding mode is it?
1: I have a HTTPS server and I added hooks in RSA decryption procedure to dump error RSA input(client key exchange).
2: I get some RSA input that I couldn't check padding successfully(It's usual) and ...
2
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0answers
319 views
RSA signatures that allow hash to move around in block
I'm looking at a broken RSA signature padding implementation in a real device. It's a very-badly implemented version of PKCS #1-like encoding, but before PKCS added the DER-encoded hash identifier.
...
2
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58 views
Does secure LWE implementation leak bit information?
We know RSA leaks one bit about the factors and improper yet secure implementations of Discrete Logarithm leak one bit about the discrete logarithm. Does LWE leak any information?
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Textbook RSA: Public key used to decrypt ciphertext and checked against known plaintext
In textbook RSA with no padding schemes, is it possible to forge a ciphertext that decrypts to a known plaintext when the ciphertext is encrypted using the private key and decrypted with the public ...
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113 views
RSA - find d,e with restrictions
For academic purposes, assuming $n, p, q$ with $n\approx 2^{4096}$ and $p,q\approx 2^{2048}$.
I need to find ($e,d$) such that:
$e$ is smaller than $2^{64}$
$d\approx 2^{4096}$ and will have as ...
2
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0answers
140 views
Estonian e-voting, vote verification system
I believe I do understand the basics of how the Estonian e-voting system works, but I'm stuck at their vote verification system. In order to get the vote verified, a client needs to encrypt all of the ...
2
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0answers
201 views
Montgomery modular multiplication – confusion with subtraction of modulus
I'm reading the paper “COMPARISON OF SCALABLE MONTGOMERY MODULAR MULTIPLICATION IMPLEMENTATIONS EMBEDDED IN RECONFIGURABLE HARDWARE” (PDF) on hardware algorithms for montgomery multiplication for ...
2
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355 views
Attacks on RSA with partially known plaintext
I know modulus $N$, public exponent $e$ and have some crypted messages $c_i$, $c_i = m_i^e mod N$. I know something about each $m_i$: they have a sequence of bytes BAADF00D at offset $t$.
Is there ...
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215 views
HBCI Encryption/Decryption
I need help during implementation of C# interface (.NET framework) for encryption of messages which are sent to/from HBCI (Homebanking Computer Interface) server according to RDH-10 standard.
...
2
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Security of right-zero padded signatures with $e=3$
I am facing this question about RSA signatures and I understand that a hash encode is secure, but I was asked this:
Given the scheme based on RSA assumption.
Consider the RSA function f with some ...
2
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0answers
279 views
Asymmetric vs symmetric encryption
I am a beginner learning about encryption and I would like to ask a few questions, hoping this is the right place to ask, so please bear with me.
We have Alice and multiple clones of Bob. Only Alice ...
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0answers
47 views
Decisional Small $e$-Residue Assumption
In 2001, Catalano et. al defined Decisional Small $e$-Residue Assumption as follows:
Let $N$ be a random chosen $\ell$-bit long RSA modulus and $e>2$ a random integer such that $\text{gcd}(e, \...
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511 views
Feasible attacks on ECRSA cryptosystem
In ECRSA cryptosystem, I want to know the feasible attacks. For illustrations we have two prime $p$ and $q$ such that $p \equiv 2 \pmod 3$, $q \equiv 2 \pmod 3$ and generate key pair as follows:
$$n = ...
2
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0answers
456 views
MITM Attack on Key Exchange Protocols
I was doing research on this attack and I am wondering, why is Diffie-Hellman always
associated with such an attack? Aren't other public key cryptography schemes vulnerable
to the same kind of ...
2
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0answers
432 views
Limit the number of private key uses for RSASSA-PKCS1-v1_5 with SHA-256 signature?
Assuming all messages and their signatures are available to the attacker, is it secure to use the same RSA private key to sign many messages (roughly $10^{6}$) via PKCS#11 ...
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36 views
Are there UFDs where the factorization problem is difficult but finding irreducibles is cheap?
Factorization of integers is hard, but finding irreducibles is expensive. Is there a ring where factorization is assumed hard but finding irreducibles is much cheaper than over $\Bbb Z$?
It could ...
