# All Questions

18,184 questions
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### Verifying valid public key and finding private key? [duplicate]

A naive user of RSA has announced the public key $n = 2903239, e = 5$. Eve has worked out that $n = 1237×2347$. Verify that the public key is valid and explain why the private key is $d = 2319725$. [...
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### How to compare the order of elements in cyclic groups?

In a cyclic group with randomly looking behavior like the one used in secp256k1, is there any known efficient algorithm to compare the order of two randomly given elements $P_1$ and $P_2$ and find out ...
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### Why can´t an attacker find the key if he has the plain text, the IV and the ciphertext? [duplicate]

I am reading a book about web security and they are now talking about AES CBC. After reading the chapter I was wondering, can an attacker compute my secret key if he has access to the IV, the plain ...
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### Computing a probability

Let $(w_1,\cdots,w_l) \in (\{0,1\}^\lambda)^l$, and $r_1,\cdots,r_l$ are chosed as uniformly random from $Z^*_q$ such that $r_1+\cdots+r_l=0$ and $q$ is a large prime number. Also, Let $F$is a ...
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### Key, plaintext block and ciphertext block permutations question

Question: If a cipher’s key size is $k$ bits and its block size is $b$ bits, how many possible keys are there, how many possible plaintext blocks are there, and how many possible ciphertext blocks are ...
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### Using Tweets as a Random seed

I would like to start by saying I know nothing about Cryptography and was reading up on how to choose a random seed and this link is something that I found. What I basically understood that the seed ...
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### What is the point at infinity on secp256k1 and how to calculate it?

I hear that there should be a point at infinity on secp256k1. I wounder how to calculate it and what does it even mean. I tried to calculate it as $P_{inf}=P+(-P)$ but this gives different results for ...
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### With AES-GCM, may I use multiple tags per key?

In my implementation of AES-GCM, the key might change only once per minute. However, I wish to calculate a new tag every 6us, to reduce latency (since you have to buffer up a GCM "packet" before ...
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### How should we assess the quality of steganography?

I am asking this question instead of extending the discussion of another question (Perfect Steganography). I did try starting a chat room (https://chat.stackexchange.com/rooms/87636/perfect-...
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### Fail to Sign/Verify signinature in C# [migrated]

I am trying to use the .Net RSA functions to sign a Hash, but when i try to Sign the hash and then verify the Signed string it turns out false... Is this the wrong place to ask? (Is this more of a ...
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### In AES is 0x11b is the specified field generator? [duplicate]

As I know all arithmetic operations in AES are done over $GF(2^8)$ so I want to know which field generator AES uses? is it 0x11B? and choosing another field generator would it give a different results?...
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### One-round feistel network (DES) attack

I can't find out how to break 1 round of feistel network (obtaining the key). I understand why this equation takes place: $R_1 \oplus L_0 = f(R_0, k_1)$ EDIT: The function f looks like this: But ...
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### Does Elliptic Curve Integrated Encryption Scheme (ECIES) provide IND-CCA2 security?

I am looking for a faster alternative to RSA with OAEP as a IND-CCA2 public key scheme. Elliptic Curve Integrated Encryption Scheme might be a candidate, but I am not sure if it provides IND-CCA2 ...
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### Can AES be used with a static key?

I am making an embedded system for a project that uses AES. As I cannot accommodate key generation (hardware constraints) I am using a static key. I can use another small algorithm to create dynamism ...
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### Definition of Short Authentication String

I am studying for my cryptography final and I passed by the following term: short authentication string. Please, can anyone explain it to me, thank you very much.
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### Is There an Opensource Manual Calculation of AES-128 bit?

Is There an Opensource Manual Calculation of AES-128 bit as in Cronos I have to learn calculations manually.
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### Magic Number to calculate number of rounds for M-R in FIPS 186-4

In Fips 186-4, there is an algorithm in Appendix F (at page 117 in my copy of the 2013 version) to calculate the number of rounds of the Miller-Rabin primality test to random bases. Does anybody ...
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### Comparable or partially homomorphic public key derivation for signatures?

Are there any public key signature schemes that can be compared blindly or partially homomorphically based on the private key without knowing the private key? Example: let's say I derive a public key ...
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### AES-128 8th round bit fault propagation

It's well known that by injecting a byte fault during the 8th round of AES 128 just before the mix column the key can be recovered with $2^{32}$-key space. A brute force attack is then possible but ...
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### What is meant by the term “hostile environment”? [closed]

I come across many time a term called ”hostile environment” in cryptographic literature. What does “hostile” mean exactly? Is it unknown third parties which are responsible for handling and routing ...
181 views

### why do we asume that in the registration process communication is over the secure channel?

I was reading some research papers and saw that in Registration phase/process it is always assumed that communication is over the secure/private channel, whereas, all of the phases communication is ...
198 views

### What is Perfect forward secrecy?

I have read that when a user contacts an entity like a bank, it creates a pre-master key and then selects a master key for subsequent communications. Can the lack of PFS, create a security flaw if ...
380 views

### Where would a “half round” come from?

In the hierocrypt-L3 description, the cipher takes 6, 7, or 8 rounds. Example source code also seems to follow this same specification of 8 rounds for 256-bit keys. Wikipedia shows 8.5 rounds for ...
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### RSA2048 smallest possible modulus

what is the smallest possible modulus for RSA2048? I generate a random data with I want to encrypt by a textbook RSA2048 and I'm not sure where the first 1-bit should be. According to OpenSSL source ...
92 views

### What is the use of SCRAM-SHA-256 (over SCRAM-SHA-1)?

The Salted Challenge Response Authentication Mechanism (SCRAM) specified in RFC 5802 can use arbitrary hash functions to operate. The base version from RFC 5802 uses SHA-1. From my understanding, ...
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### Why Random Secret Necessary Almost in all digital Signature Algorithms

I've read some introduction documents about digital signatures, and all they said is Signer calculates a hash of data to be signed. This hash is encrypted with the private key. Verifier reads the ...
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### Using zk-snarks to check if value is greater than another

Can I use Zk-SNARKS to prove that a given secret value is greater than another public value. for Example to prove that secret_value >10 . if so How would such a circuit look I am using snarks.js ...
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### Is there a way of “bitwise” decrypting a corrupt Bitlocker encrypted raw HDD-image [migrated]

I'm facing a situation, where I'd like to decrypt a "corrupted" Bitlocker protected drive (Windows 10 Partition) by using the known 48-digit recovery key. Corrupt means, I executed a restore (Windows ...
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### What is modulo switching, in a nutshell?

Coupled with the terms bootstrapping and relinearization, the term modulo switching appears a lot in the FHE literature. What is it and how does it relate to the other two?
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### Generation of a symmetric encryption key in TPM

I know that keys in a TPM key hierarchy are encrypted with their parent keys. And I read that those parent keys (for instance an asymmetric SRK) need to have some symmetric secret for said encryption. ...
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### Lightweight block ciphers that support decryption with minimal overhead?

Lightweight block ciphers are mostly expressed for encryption routine and efforts are made to keep it as light as possible mostly in terms of gates count and power usage although some try to keep ...
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### 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 ...
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### Continuous logarithms in cryptography

Cryptographic procedures seem to almost exclusively use discrete logarithms rather than continuous logarithms. Hence, I assume there are good and sound reasons for this. In essence, answers provided ...