# All Questions

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### Does the security proof of HMAC somehow change if it's instantiated with sponge-based hash functions with small rate and large capacity?

HMAC was introduced in [1], as a MAC that has its security proof based on the properties on the underlaying hash function. The hash functions considered in that paper were ones based on the Merkle-...
11 views

### Why all multivariate schemes restrict themselves to polynomials of degree 2

If we note all multivariate schemes restrict themselves to polynomials of degree 2. I was wondering why they do it. After looking on the internet, I came to know that they do it for the efficiency. My ...
37 views

### Is a stream cipher and a (cryptographically secure) PRNG nearly the same thing?

If I let the authentification tag aside (which is important), encrypting with AES-GCM and a fixed key and nonce: ...
17 views

### Parallel random-access machine resistance in memory-hard functions

I'm trying to add memory-hardness to a hash function. A link to the specific line where that part of the implementation starts can be seen here. The basic approach is this: (1) Concatenate a string of ...
36 views

### byte significance with hash functions

I am using the python hmac module to generate an authentication code. Given a key, message, and hash function (I am using md5), the library returns an authentication code as a python bytes object. I ...
10 views

### How to restore the original mnemonics from shares? [closed]

I just read that an original mnemonic can be split into parts, I am a little confused about how the system can restore the original mnemonic from these mnemonic pieces. example i have mnemonic ...
24 views

### Can a nonce be used to steganographically hide a message?

If a standard encryption scheme involves a nonce, as most do, can the nonce be used to hide another small message? That is, the nonce (rather than being randomly generated) is a hidden message XORed ...
4 views

### How to create certificate signed with RSAPSS using openssl command? [migrated]

I tried https://gist.github.com/superseb/788a234647324b49ee5a56e07e3a91ac for commands, but getting following error in first command itself: ...
19 views

### Homomorphic encryption watermarking identity

I've been doing some research on FHE and SWHE schemes, most specifically on watermarking. As far as I've understood, you take as the merchant, take the buyer information encrypted and his public key ...
43 views

### Is is safe to use MtEtM? (MAC-then-Encrypt and Encrypt-than-MAC)

Assuming I am using different secrets/keys for each MAC pass, does running both MtE and EtM creates any vulnerability? This is what I mean about doing MtEtM: ...
25 views

### How does Merkle tree Bitcoin query works?

I am trying to understand the basics of Encryption and Decryption in the Bitcoin blockchain. However there is something which is scratching my head recently? I understand how The Merkle Tree hashes ...
110 views

### Tests to distinguish between PRNG and a CSPRNG

What are the tests which a regular PRNG would fail but a CSPRNG would succeed? Is it just the next-bit test or are there multiple other tests which a PRNG which is not a CSPRNG would fail? Would a ...
20 views

### $\mathrm{Hash}(A\|B)$ where $B$ is known, $A$ is unknown. Would knowing $\mathrm{Hash}(A\|C)$ as well as $C$, speed up a brute force search for $A$

Let's say $\mathrm{Hash}(A\|B)$ is a hash of two concatenated strings, $A$ and $B$. Suppose I am trying to figure out $A$ from $\mathrm{Hash}(A\|B)$, I know $B$ but not $A$, I want to brute force to ...
30 views

### Understanding Blockchain technology especially Wallet related

Hey guys I'm trying to really understand how blockchain technology works. To understand it completely I am trying to code a new coin, not sure if I'm doing it right. I came across the concept of ...
42 views

### Perfect Secrecy and Message distribution

I have been trying to come up with a proof of the following statement, Suppose a cryptosystem achieves perfect secrecy for a particular plaintext probability distribution then Prove that perfect ...
26 views

### Right implementation of digital signature with timestamp

The goal is to sign a file along with a timestamp using ECDSA. The signature can be later used to prove the file existed at a particular time. Signing implementation. The timestamp is appended with ...