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How to attack CBC and OFB by knowning plaint-text and its cipher-text?

In the CBC and OFB encryption with fixe IV and by knowing the plaint-text and its cipher-text how we can decrypt the other cipher-texts? Thank you
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1answer
22 views

Is it secure to use ECDSA for any arbitrary point on the Elliptic Curve as the Generator point?

My question concerns the elliptic curve $E$ over a prime field $\mathbb F_p$. To the best of my understanding, ECDSA requires a Generator point $G$ of prime order $n$, and the $r$ and $s$ values of ...
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0answers
9 views

Implementation of designated verifier signature success sometime and fail sometime [migrated]

I am trying to implement JSO Designated Verifier Scheme by Java. I follow the paper above to implement it. But I get a very strange result, which sometime the verification is success and sometime fail....
1
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1answer
131 views

For Diffie-Helman, why is a g value of p − 1 not a suitable choice?

I am currently learning about the Diffie-Helman key exchange. I understand that for a $g$ of $1$, you're resulting key would always end up as one which would obviously not be secure. However, I read ...
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0answers
37 views

Finding out cryptography method used and decrypting it [closed]

I used Frida to do an MITM attack on an android app and I was able to successfully record network transmissions but there was one problem, all the requests sent to server was encrypted. Then i tried ...
1
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1answer
46 views

Licensing software with asymmetric signed files

NOTE: I know that there are numerous topics here on StackExchange about this but I've read them all and this question still persists. I'm currently working to enhance the security of a windows based ...
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0answers
25 views

Cracking a Shift Cipher that uses an Unknown Deterministic Scheduling Algorithm

Consider a shift cipher that has the following encryption scheme: The plaintext contains lowercase characters and spaces, is composed of English text, and is about length 500. Thus, the message (and ...
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0answers
14 views

Decrypting data on client side for use inside program

So I am developing a python program and encrypting the trained machine learning models which need to be decrypted when loading them on client side. My program will deployed on the client's machine ...
0
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1answer
48 views

About Logjam TSL Attack

As the Logjam attack allows a man-in-the-middle attacker to downgrade vulnerable TLS connections to 512-bit export-grade cryptography by modifying the ClientHello and ServerHello. Can the Logjam ...
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0answers
24 views

Trying to Understand Ring Learning With Error Encryption

I'm trying to understand the following RLWE encryption scheme from this Chris Peikert's paper Say i choose $q = 97$, $n=8$ and the polynomial $a = 96 x^8+30 x^7+76 x^6+12 x^5+57 x^4+77 x^3+70 x^2+49 ...
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0answers
25 views

Finding a hash function that calculates average of an item in a stream of tuples

So, I have a stream of tuples coming in for example [country, state, person], where state and person are unique items. Now I have to find : 1. for each country, I have to estimate average number of ...
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0answers
28 views

Is there a cipher that encrypts words into different words?

I've been looking at the various types of ciphers and I can't seem to find something I want or if it's even possible. For example the text is "London2234", when run through the cipher, it encrypts ...
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0answers
23 views

Fastest XOR operation using either C or C++ [migrated]

I am trying to XOR two files each 1Mb which contains only 0 and 1. It works, but I think it is very slow for the C++ program - approximately 4 sec. Could someone, please, suggest the fastest XOR ...
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2answers
52 views

What is the use of a nonce in public-key encryption if it's meant to be shared?

I'm using PHP. The guys over at paragonie have made encryption easy for the PHP eco-system. Now, on my computer, Alice, when I ...
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0answers
61 views

Finding a dataset to benchmark cryptographic algorithms

I’m planning to compare cryptographic algorithms in terms of encryption/decryption time, memory used etc. and for that I’m in need of a standard dataset consisting of plaintexts of different bit sizes ...
1
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1answer
27 views

Integrity of format preserving Encryption

In this question regarding integrity of FPE, the main point of the answer is that: FFX is not malleable. [...] FFX can provide integrity protection in very limited circumstances. So I was ...
1
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1answer
41 views

Secure enigma machine?

The enigma machine had a serious flaw: the letters could not be encrypted as themselves. Is there an online enigma simulator I can try that does not have this flaw, which would likely make it secure?
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1answer
65 views

PAKE password change

Is there any way to change a password using a PAKE-like algorithm, without the server getting the plaintext of either the old or new password?
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1answer
33 views

Why encrypt symmetric keys first with RSA and then the private-key with a PW?

In for example the Microsoft Encrypting File System, the SYM-Key is first encrypted with a RSA-Pub-key and its corresponding private-key is then encrypted using a users password. Why not encrypt the ...
5
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1answer
56 views

Use large key size for RC4 to avoid RC4 bias

I saw a question on StackOverflow where RC4 was initialized by a 1024 bit key (with 2048 the maximum key size, if I'm not mistaken). Will such a large key size possibly solve any of the bias of the ...
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0answers
21 views

Understanding signature length computation

In the following paper, the authors provide a lattice-based ring signature from a 1-out-of-N proof, copied below. They illustrate their discovery with a table on the bottom of page 28, summarizing ...
1
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1answer
31 views

Securely “forwarding” a Large message in a hybrid encryption system without sending the actual message

Alice has symmetrically encrypted the large (100Mb) MessageA with a random key K1, and then asymmetrically encrypted K1 with Bobs public key. She then stores the encrypted large message in a central ...
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0answers
35 views

Fully Homomorphic cryptographic Scheme?

Given two FHE schemes FHE1 and FHE2 in which one of the two scheme is secure and other is not (we have no idea which is secure). Construct a FHE scheme which is secure using the given two scheme.
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0answers
25 views

How to implement division operation on ciphertext by using HElib or SEAL?

HElib has no general purpose API for number operations such as comparison or division. How can we implement division operation on ciphertext?How to encrypt floating numbers of any length in ...
0
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1answer
36 views

Replay attack resistant MAC?

I came up with a threat model where: Alice and Bob agree on a shared key $K$ Alice sends a plain text $M$ and its $\operatorname{MAC}$ tag, $T = \operatorname{MAC}(K,M)$ to Bob over an untrusted ...
0
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1answer
32 views

What algorithm for AES key wrapping to choose in an embedded environment

In an embedded environment, what AES key wrap algorithm is best, in terms of performance and security coverage? We are using RSA PKI asymmetric encryption.
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0answers
18 views

How to decrypt Vigenere Cipher message with no key and using frequency distribution table? [closed]

1) Illustrate the Vigenere Cipher technique: Encrypt the English message below with the key (ABCD), Message: CRYPTOISSHORTFORCRYPTOGRAPHY 2) Suppose in the receiver end, you do not have the ...
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0answers
16 views

How does AWS service verify the identity of the sender?

My question is regarding to : How does AWS Secret key and access key work The point 5: AWS service verifies the identity of the sender and integrity of the message by recomputing the HMAC code....
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2answers
37 views

How to design a secure challange-response authentication protocol?

I am implementing a custom challenge-response protocol to authenticate a client to a server. Mutual authentication is not required, i.e. the server doesn't need to be authenticated to the client. The ...
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0answers
30 views

Old puzzle from different universe [closed]

Nerson Renda Corsa Tales Argonyk Coli Walen Veris Barcam Ypex Selem Ashiray Cype Fazle Epartalis Namil Skargut Debly Caran Flin Its encrypted message i can't decipher. I think it may be created ...
1
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1answer
49 views

Permutation of first $k$ prime powers as a one-way function?

Let $a_1$ through $a_k$ be some permutation of the first $k$ primes. Let $n \in [1,k!]$ be a parameter specifying the exact ordering by taking the $n$th permutation in a sorted list or by some other ...
1
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1answer
58 views

Proof of possession. x25519 + ed25519

There are Client and Server. Client have previously send public keys for x25519 and ed25519 to the server. And now need to prove that it has private keys for them. I have found similar solutions in ...
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0answers
21 views

decrypting a message encrypted in 128 AES ECB using a shared key [closed]

I am trying to read a message sent from a server to a client which have a pre-shared private they start by each sending random nonce encrypted with the key and use the decrypted nonce to make a ...
4
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0answers
36 views

Decision to Search LWE when modulus $q=p^e$

I am reading Applebaum et al.. In Lemma 1. (page 7), Applebaum et al. proved the decision to search reduction when the modulus $q=p^e$ for prime $p$. In the proof, they define the hybrid ...
2
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1answer
43 views

Is the EdDSA signature scheme provable security?

The EdDSA signature scheme is a deterministic scheme. So could it be proven provable security in Random oracle model?
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0answers
23 views

Errors when decrypting using ECIES across platforms? [closed]

I'm seeing an intermittent error decrypting content when using ECIES: So far it seems to occur 1/5 or fewer times (I need to dedicate some time to better characterize the failure rate with more ...
0
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2answers
58 views

Cracking hashes: With vs without knowing the salts

Let's assume the following situation: The attacker has extracted 1000 password hashes from a website (vuln.com) along with all their usernames and hashing ...
0
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1answer
63 views

Is there an efficient algorithm that allows to construct a cryptographically secure $n$-bit hash function based on two unkeyed $n$-bit permutations?

Let $f(x)$ and $g(x)$ denote two independent, “ideal”, unkeyed, public $n$-bit permutations (two publicly known bijective functions that produce $n$-bit outputs from $n$-bit inputs), where $n$ is an ...
2
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0answers
55 views

How do byte-sliced AES implementations work?

While I understand the principle of bit-slicing, several papers mention byte-sliced AES implementations (see e.g. Homomorphic Evaluation of the AES Circuit and Fast Implementations of AES on Various ...
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0answers
38 views

can deep learning simulate an algorithm? [closed]

I will begin with a simple example to illustrate my point. Consider a known data set consisting of two columns ...
3
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2answers
45 views

Is the encryption more secure if we apply Pohlig-Hellman cipher twice with different keys but with the same modulus?

To encrypt a message $M$, we compute $C=M^k \bmod p$ and to decrypt a Cipher-text we compute $M=C^{k^{−1} \bmod (p−1)} \bmod p$ But if we use Pohlig Hellman twice like $C_1=M^k \bmod p$, and then $...
0
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1answer
64 views

Using SHA384 as an asymmetric cipher?

SHA384 is a hash function that can be (and is) used to verify data by checking it. Can it also be used as the background for a public-key crypto system? Here is what I mean: A 48-byte string is ...
1
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1answer
82 views

How to Sample from Frobenius Eigenspace?

So I was implementing the $2$-point method described here[1], which requires to samples two points $P_0, P_1$ in the Frobenius eigenspace initially. It uses a method called Elligator, which seems to ...
1
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0answers
46 views

libgcrypt and rdrand usage

for some reasons, i was looking into libgcrypt source code and found this : https://github.com/gpg/libgcrypt/blob/b64b029318e7d0b66123015146614118f466a7a9/random/rndlinux.c#L189 if i understand this ...
0
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0answers
61 views

How can I prove a truncated hash fuction need not be collision resistant?

Let $H : \{0, 1\}^∗ \mapsto \{0, 1\}^ n$ be a collision-resistant hash function. Define $H_0(M) = H(M)\mathbin\|0^{n−10}$. That is, $H_0$ appends ($n − 10$) zeros to the output of $H$. Clearly $H_0$ ...
5
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0answers
26 views

Relation between LPN and GAPSVP?

I have a question regarding the relationship between the (search) LPN problem and the GapSVP problem. I have read a related problem that explains the main theorem in Reg05: the GapSVP problem can be ...
0
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1answer
30 views

Decryption in Goldwasser-Micali Scheme

Referring to the following URL: http://cryptowiki.net/index.php?title=Goldwasser_Micali_cryptosystem The decryption of the message is based on wether the bit is a QRn or not, but how do we know/...
2
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1answer
86 views

Finding the IV values of SHA-256 given all message blocks

Given all message blocks $w[i],i \in 0:63$ and assume that $n<128$ (arbitrary) bits $x_1,x_2,...,x_n$ of the IV values are unknown (e.g., $h_7$ bits are unknown) while other IV values coincide with ...
3
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1answer
72 views

Insecure MAC built on pseudorandom function

this is a question about Katz-Lindell book, introduction to modern cryptography, 2nd edition, exercise 4.7, part c. For (a) and (b) it is clear that the Macs are insecure, but for (c) I am struggling ...
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0answers
34 views

How to forge a signature in a custom PMAC implementation

From a crypto challenge i have the following PMAC variant where the task is to forge a signature to fulfil a specific condition: Preparation: in the finite Field GF(2^128) with the polynomial x^128 + ...

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