3
votes
0answers
107 views

How secure is $\operatorname{AES256}_{\operatorname{ECB}}(\operatorname{ChaCha20}(\text{plaintext}))$?

Suppose I encrypt a bytestream using ChaCha20, and then encrypt the resulting ciphertext using AES in ECB mode. How secure is the combination?
3
votes
0answers
42 views

Can you give me a summary of cryptographic hardness assumptions?

Until recently, I had a link to a website which summarizes up-to-date cryptographic hardness assumptions. But, unfortunately I cannot find it. The webpage is categorized well problems such as, DL ...
3
votes
0answers
34 views

Best Attack Against HFE cryptosystem

I am looking for the best know attack against HFE cryptosystem. Reading this paper DEGREE OF REGULARITY FOR HFE I found the next claim However, Faugere and Joux demonstrated that we can solve and ...
3
votes
0answers
52 views

Are there any crypography schemes which rely on Graph Isomorphism not being in P?

Are there any cryptography schemes having correctness relying on Graph Isomorphism not being in P? If I should ask this question in the CS Theory area, I will migrate it. Thanks.
3
votes
0answers
37 views

Cloneability of AES-128

I would like to implement an anti-counterfeiting scheme for tools my company manufactures. This would ideally be done via RFID/NFC tags. However, the environment in which these tags operate would ...
3
votes
2answers
134 views

What is a purpose of reducing lattice basis?

This may be too broad question but it is not. I have been studying lattices for few months now, more specifically I studied: lattice problems ($SVP$, $CVP$ and etc.) lattice cryptography in post ...
3
votes
0answers
94 views

Finding sum of two encrypted numbers

Let's consider such process: Two emitents emit two (integer) secret numbers independently They encrypt (encode) these number in such a way that no-one (except emitent) can decode these numbers. ...
3
votes
1answer
41 views

The solution of insert MAC in a ciphertext without Authenticated Encryption supported

From Should we MAC-then-encrypt or encrypt-then-MAC?, I understand I should do Encrypt-than-MAC, which the MAC included all the information such as IV and cipher text. After reading Why choose an ...
3
votes
1answer
89 views

Authenticated encryption with Signatures

I've given a CPA secure private key encryption scheme (wich gets to a CCA secure scheme or better to an authenticated encryption scheme, when i combine it with a given MAC) and a unforgeable public ...
3
votes
0answers
17 views

security of Even-Mansour scheme with keyed shuffle

I was researching the Even-Mansour scheme and had a question that wasn't addressed in the paper that I saw, and google was minimally helpful. What if a permutation that uses secret data like the ...
3
votes
0answers
33 views

Breaking linear blockcipher - expanding recursive formula

I am trying to break a block cipher that can be defined as follows: We have 12 rounds and at each round we perform the following operation. We split 64 bit data into 2 parts each 32-bits, $\ x_r$ ...
3
votes
0answers
29 views

Publishing only items your subscriber previously subscribed to, without you knowing which those items are

Let's say you were given a dump from a security breach. You want to share the email addresses affected by the breach with a separate company who pays you for this service so that they can protect ...
3
votes
0answers
40 views

Would LWE problem be still secure if error were like this $e=2e_1$?

In the Learning with error problem, if the error term $e$ from equation $b=<a,s>/q+e$ were of this kind $e=2e_1$, where $e_1$ is chosen according to the probability distribution for the LWE ...
3
votes
0answers
92 views

Unlinkability of Merkle-Damgård hash function results

Question: Are multiple outputs of a Merkle-Damgård hash function (or specifically SHA-256, if this can only be said for a specific algorithm) on unknown data unlinkable? If yes: Can this be formally ...
3
votes
0answers
31 views

What is the current encryption method used on GSM currently?

I am currently doing a mini project which sniffs GSM packets using gr-gsm and wireshark. I was wondering if anyone knows what is the name of the current encryption algorithm method used on GSM?
3
votes
0answers
30 views

how exploitable are cache timing attacks

So there's a PHP package that's been recently written to protect against cache timing attacks: https://www.reddit.com/r/PHP/comments/4a1iuh/rfc_4648_character_encoding_written_to_resist/ My question ...
3
votes
0answers
58 views

Perfect secrecy is maintained for other plaintext prob distributions?

Suppose a cryptosystem achieves perfect secrecy for a particular plaintext probability distribution. Prove that perfect secrecy is maintained for any other plaintext probability distribution. Having ...
3
votes
2answers
26 views

X509 converted to Encrypted and Signing keys

We have proprietary tool which takes a p12 file and generates a .key file. Inside the key file, I see two PEM formatted sections: Encrypting Certificate and Signing Certificate. When I open them on my ...
3
votes
0answers
73 views

How common are weak RSA keys?

There exist certain attacks that can be used against RSA keys whose prime factors are of specific forms, such as one by Coppersmith. How common are these RSA keys? If you generate primes randomly, ...
3
votes
0answers
22 views

Can GCM auth be bitsliced?

Is it possible to use bitslicing for GCM? This seems like a way to allow for a way to avoid cache-timing attacks without PCLMUL instructions and with good performance.
3
votes
0answers
38 views

DES_cblock and Key Recovery

I'm trying to get my hands on the key that OpenSSL uses for a DES encryption. The key is based off a random number generator with a seed taken as parameter. The code used is below, provided as part ...
3
votes
0answers
44 views

How to make a “zero knowledge” cache/key-value store

I'd like to use a possibly insecure cache for storing expensive-to-calculate sensitive information. My requirements are: If the cache ever gets compromised it should reveal nothing about its ids or ...
3
votes
0answers
28 views

Can I get an explanation of HDCP's key exchange protocol?

I'm talking about HDCP v1.x. The specification is a too dense for me and easy-to-understand information about it on the net is scarce. What I've gathered is: that there is a master key that is a 40-...
3
votes
0answers
21 views

Would using a symmetric list of subkeys in a Feistel cipher make our messages vulnerable to oracle attacks?

Suppose I have a Feistel cipher structure that has $16$ rounds. I come up with $8$ subkeys $k_1,k_2,...,k_8$ to be used for the first $8$ rounds and then assign the rest of the keys so that $k_9=k_8,...
3
votes
0answers
32 views

Access structure in Attributes Based Encryption [duplicate]

I thought that access structure and access tree are equivalent but I've read in a paper (page 3) that there are at least three types of access structures : AND gates Access tree LSSS generating ...
3
votes
0answers
102 views

What is the difference between mutual authentication and unilateral authentication both ways?

I am currently reading Engineering Security by Peter Gutmann, on page 7 he states: proper mutual authentication is quite different from unilateral authentication in both directions He ...
3
votes
1answer
66 views

The sign of the correlation in linear approximation

${\text{Let }}g:{\{ 0,1\} ^n} \to {\{ 0,1\} ^n}$ be a round function of an $n$-bit iterated block cipher and let $K \in {\{ 0,1\} ^n}$ be a fixed round-key, and denote ${g_K}(x) = g(x \oplus K).$ Show ...
3
votes
0answers
33 views

no speedup from preprocessing in blynn's PBC library

I am implementing some pairing-based cryptography protocol using blynn's PBC library. I am only at the beginning and I wanted to confirm that preprocessing does increase the speed. However I seem to ...
3
votes
0answers
67 views

LR-Oracle Experiment in Lindell and Katz

In reference to the LR-Oracle experiment in “Introduction to Modern Cryptography” (2nd edition) by Lindell & Katz, Definition 3.23 states a scheme $\pi = (Gen,Enc_K,Dec_K)$ is CPA secure for ...
3
votes
0answers
65 views

Why reveal MAC-keys after using them?

As far as my understanding goes MACs are used to determine whether the received message comes from a source that has access to a MAC-key which is known by both parties. Some crypto protocols reveal ...
3
votes
1answer
161 views

end-to-end encrypted chat app with symmetric + public key encryption, TLS and cert pinning

A big drawback of end-to-end encrypted messaging services is that, as soon as you lose your device, you lose all your messages. Your private key is gone after all. I was wondering though, wouldn't it ...
3
votes
0answers
86 views

TPM's monotonic counters

I am reading the TPM Design Principles v1.2 §17 and do not feel I fully understand the example they give on how the counters would work. Apparently monotonic counters are used to prevent replay ...
3
votes
0answers
34 views

Is EFS vulnerable to Chosen plaintext attack?

I have some backed up files encrypted with EFS and I lost the EFS certificate thus unable to decrypt the files. I understand that EFS uses the user certificate public key to encrypt the symmetric key (...
3
votes
0answers
65 views

High-level overview of system architecture of LUKS/cryptsetup (how it works vs. how to setup) [closed]

I've been searching (unsuccessfully) online for a high-level overview of how LUKS/cryptsetup disk encryption works. I am reading through the cryptsetup source code to try to understand what is going ...
3
votes
0answers
90 views

HD (Hierarchical Deterministic) Keys using Safe Curves?

Bitcoin's HD (Hierarchical Deterministic) Keys as described in BIP32 allow for a master key to be created (a private key and a chain code) such that a tree of both public and private keys can be ...
3
votes
0answers
35 views

Seeking an implementation of the Satoh algorithm for elliptical curve point counting

I would be very grateful if someone has an implementation of the Satoh algorithm (Fast Elliptic Curve Point Counting). Can someone point me to practical algorithm implementations or provide some ...
3
votes
0answers
50 views

Cost of attack on DSA with attack on DLP

Are there any (recent) estimates of cost of attack on DSA by solving the discrete logarithm? I'm especially interested in attacks that use Pollard's rho algorithm. Are there any optimized ...
3
votes
0answers
49 views

How does darkmail (DIME) work to hide email metadata?

While Email encryption can protect the content of an email, the metadata are still readable and can be used to gather important information about the sender and the receiver. There were several news ...
3
votes
0answers
50 views

authentication protocol questions/security

Disclaimer: I am the only person that uses my software. This is just experimental fun. I previously wrote a server/client that used the secure remote password protocol authentication. I had an idea ...
3
votes
0answers
97 views

Implementation specific differences between RDRAND and RDSEED

I've read Intel's The Difference Between RDRAND and RDSEED and Intel Digital Random Number Generator (DRNG) Software Implementation Guide, but I have some open questions that are specific to usage in ...
3
votes
0answers
82 views

Lattice attacks against Multilinear Maps [CLT13]

I am currently studying an article on a construction of Multilinear maps. There are some attacks on the scheme presented by the authors and I got stuck at the one in section 5.1. I will try to ...
3
votes
0answers
55 views

How about a homomorphic integer sorting in a MPC context?

I want to implement the ATV-FHE scheme as described by Adriana López-Alt, Eran Tromer, Vinod Vaikuntanathan: On-the-Fly Multiparty Computation on the Cloud via Multikey Fully Homomorphic Encryption (...
3
votes
0answers
86 views

Brute force attack multiple stream cipher

Assume that a scheme used to secure a specific system $Π=(Gen,Enc,Dec)$ which is thought have indistinguishable multiple encryption in the presence of an eavesdropper. For any adversary $A$ that can ...
3
votes
0answers
50 views

Elliptic Curve Blind Signature Implementation

I have seen this prior post: Elliptic Curve based blind signature implementation Currently I'm sizing up how difficult it would be to attain Elliptic Curve Blind signatures for an application I'm ...
3
votes
1answer
116 views

TLS RSA Certificate with Elliptic Curve Negotiation

When I look at Google's Public Key in Firefox I get PKCS #1 SHA-256 With RSA Encryption Yet according to SSL Labs Google has EC 256 bits / SHA256withRSA and supports ...
3
votes
0answers
141 views

Are there key collisions in AES-192, AES-256?

Suppose we have a single, fixed plaintext block $p$ of 128 bits. Call the set of all possible 128 bit blocks $B$. We could define fixed plaintext AES-128 as a function $f(k) \to B$ that takes a 128 ...
3
votes
2answers
118 views

Is this a correct way of use symmetric encryption?

If I want to encrypt some block of text in AES, but at the time of decryption I don't have a way to check if the symmetric key is the correct one. So I: Generate a randomKey, and use that to encrypt ...
3
votes
0answers
490 views

Which is/are the strongest known Fully Homomorphic Encryption scheme(s)?

As it is discussed here that the highest security any homomorphic encryption scheme is at most IND-CCA1, Is there any known fully homomorphic encryption scheme that achieves this security level? Out ...
3
votes
0answers
46 views

How to test a FHE implementation?

I want to implement a FHE scheme based on NTRU, namely the scheme described here https://eprint.iacr.org/2014/039.pdf . How to test the security of my implementation ? Do I have to implement the ...
3
votes
0answers
66 views

Unknown authenticated encryption mode

I'm running through a protocol specification (LoRaWAN, pdf), and I'm puzzled by the crypto. The data is encrypted and authenticated in the following way: a unique 128-bit key is used; the plaintext ...

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