# All Questions

23,029 questions
Filter by
Sorted by
Tagged with
50 views

### Choosing a suitable prime for accumulators

I am trying to work out accumulators and generate $S = \{ e_1,e_2 \ldots, e_n \}$ from this (Section 3.4 - Choosing a Suitable Prime). For each element of $e_i$ compute its representation $x_i$.(This ...
27 views

### Need for DHKE in TLS [duplicate]

Why does TLS as used in https need DHKE? Since the server presents a certificate with a public key, can that not be used for session key establishment? The client (browser) can generate a session key, ...
7 views

### What will be the key size for rsa, ecdhe and ecdsa from the cipher suite given? [migrated]

From the cipher suites tls_rsa_with_aes_128_cbc_sha256 and tls_ecdhe_ecdsa_with_aes_128_cbc_sha256 how do I know what will be ...
28 views

### Changing a bit in IV of MD5

It is obvious that changing even one bit in data or IV (initialization vector) will change the hash value a lot. I want to know if, for example, changing a single bit within the $IV$ in MD5 can be ...
23 views

### Multi signature encryption (multiple people can decrypt)

I understand that multi sig transactions exist so that X of N need to sign to release a transaction. If only 1 of N is required I guess any of the recipients can spend. This made me wonder, is it ...
118 views

### Identify AES Mode

Let's say I have an API that accepts Plaintext and IV as input parameter and returns the ciphertext. I know that API is using AES 128 encryption but now I need to identify which encryption mode (ECB, ...
39 views

### Hashing of variable-length chunked data leading to leakage of secret key from side channel?

Hypothetically, secret data could be hashed in some schemes in one way or another. Could chunking of the data lead to exposure of secret component through side channel? Say converting a randomized ...
27 views

### Re-encrypt modified file section with AES-CTR

I am trying to encrypt a file using AES/CTR/NoPadding. The goal is to re-encrypt the new/changed blocks and leave the old ones unchanged then generate a new MAC. My thinking is that when the file ...
21 views

Decrypt the ADVGX code, without a keyword or matrix. FGGAADXXFAXFGGAGAGAAFDXXXAFGFGGGFXGXXAGGFXGDAGFX Important Hint:
55 views

### SHA3-512 similar message digest

How is it possible to find a similar message-digest for SHA3-512 for the first 80 bits or so? There was a Q/A on this site where the answer stated that 80 bits that $2^{42}$ computations are required. ...
38 views

### Random salt and PBKDF2 key

Suppose I wrote a function $$(salt,IV ) = \text{keyIVGenerator}(passwd)$$ which generates a random salt of size 32-bytes and a random Initialisation Vector (IV) of size 16-bytes. Then, use a Key ...
33 views

### The following is question. I missed a class and thus am unable to solve it. Someone help me please [closed]

The DHKE (Diffie-Hellman key exchange ) is done in the GF(2^5). The irreducible polynomial is P(x)=x^5+x^2+1. The α value is x^2. If the private keys of a=3 and b=12 what is the session key Kab?
29 views

### Does anyone know the encryption of this data? [closed]

I'm analyzing a game packet and I would like to know if anyone knows the encryption used here, because I don't know if it was the company itself that built this algorithm or it's some algorithm that I ...
30 views

### Can XEX or XTS modes be used with only one tweak? (part 2)

This question is similar to Can XEX or XTS modes be used with only one tweak? except I am interested to know if one can instead use $X = E_{k}(0) \otimes \alpha^j \\ C = E_{k}(P \oplus X) \oplus X$ in ...
30 views

### What is the most efficient 1-out-of-N Oblivious Transfer construction described in current literature?

I have been studying Oblivious Transfer for my bachelor's thesis and have been surprised at the number of variations of OT. From what I've read so far, the constructions proposed by Naor and Pinkas in ...
51 views

### How to increase Poly1305 performance?

I was analysing the Chacha20 algorithm and the Poly1305 MAC generation from RFC 7539. It seems that the Chacha20 is quite faster compared to AES on CPUs without hardware support like AES-NI. But ...
20 views

### Can zk-SNARKs prove satisfiability for NP-hard languages?

In general, I think of zk-SNARK circuits representing a language in NP, meaning it is "computationally easy" to verify. However I was reading about a recent zk-SNARK (Sonic) which has as ...
17 views

### Threshold schemes

I am looking for a reference that lists all major $(n,k)$ secret sharing schemes. Can anyone help me get such a reference?
42 views

### finding second pseudo preimage faster than brute force

As far as I know finding second preimage of a hash function is almost as hard as finding preimage. But I want to know that is there any way to finding second pseudo preimage faster than brute force? I ...
117 views

### Designing a secure UDP-based communication protocol

SUMMARY UPDATE: I have changed the title of this question from "Using an encrypted packet counter as a counter value in AES-CTR" to "Designing a secure UDP-based communication protocol&...
35 views

### Can I derive IV, if I know Encrypted Txt, Key and Encryption Method?

I want to know is there any way to derive the initialization vector, if I know all the other details. AES SHA 256bits CBC pkcs5padding Input: Hello Key: 123 Output: xORGCDL88sa8cUrK8JNSCQ== Now, how ...
27 views

### Exchanging key material between HSMs of different manufacturers

In the future we may be setting up a system to secure a large number of symmetric (device) keys (a few million) by using HSMs. So, the keys themselves will be stored outside the HSM, but they will be ...
63 views

### How does randomized hashing defeat collision attack?

SEC#1 recommends randomized hashing when using SHA-1 with ECDSA; SPHINCS+ uses randomized hashing in WOTS+ to defeat collision attack so as to reduce signature size. How does a randomized hashing ...
47 views

20 views

### Is it necessary to prove EUF-CMA security of blind signature based on one-more type assumption？

One more type means one-more DL, one-more DHP, etc. I find many papers do the EUF-CMA security proof in this way. Is it necessary? What is the difference between proof based on one-more type ...
52 views

### Is AES-GCM-SIV with fixed IV deterministic authenticated encryption?

Is there any functional or strong security difference beyond speed between AES-GCM-SIV with implicit fixed public IV and no additional data AES-CTR (or AES-OFB) with 128-bit IV computed per HMAC-SHA-...
28 views

### Block cipher exercise CTR, CBC and ECB [closed]

I'm trying to figure out this exercise about CTR, CBC and ECB given Encryption Matrix [29->0, 11->1, 26->2, 1->3, 21->4, 4->5, 15->6, 31->7, 27->8, 28->9, 2->10, 14-&...