# All Questions

21,086 questions
Filter by
Sorted by
Tagged with
10 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 + ...
14 views

### Can anyone help me with this code? Related to Base64 Encoding [closed]

3qqIPPNX0fxjJv/krWhw7L8P83cTm2Dm2aOHHiAfNZQG1Q/1t1zPaY7CEwZBrHIC I am guessing it is base64 encoded, however base64 decoding won't work on it. I can't figure out how to solve it.
8 views

### Using the output of HKDF directly

I am using HKDF with an IKM and salt, the OKM is used as the key for an HMAC operation. The HMAC algorithm is authenticating messages in a communications system The salt is the concatenation of 2 ...
10 views

### LSIM library based on LibScarab

In a book called: "Intelligent,Secure and Dependable Systems in Distributed and Cloud Systems" where we can find some of its pages on the following URL: https://books.google.com.lb/books?id=...
15 views

### Cipher Block chaining but with encrypting the plain text first then xor with IV

I have just learned about the CBC mode of operation and that it gives the cipher by xoring the plaintext m0 with random IV and then encrypt it with random key and I found out that the CBC is not CPA-...
27 views

### using 0 nonce for AES-CTR

so, the question is: will it be less secure if I use a random key and static zero nonce? key = random; nonce = 0;
11 views

### A variant of LPN problem

I have a question regarding the LPN problem. The search LPN problem is to find $s$ given $(A,As+e)$ I am thinking about another problem that given $(A,As+e,As'+e',s+s')$ to find $s$, where $A$ is a ...
31 views

### why Java does not support KMAC algorithm out of the box? [closed]

My question seems specific for Java since I am looking for KMAC generation in JVM. Java runtime currently supports HMAC code generation. why is there no support for KMAC out of the box? Any standard ...
16 views

### Calculate the complexity of HKDF with a 96bit salt and a 128bit key?

I have a 128bit PreSharedKey. I don't want to use it directly. I'd much rather generated a session key with HKDF + PSK + SALT = SESSIONKEY. But... I'm under strict size limits for packet size. So I'm ...
15 views

### Three Pass Protocol Question!

Alice and Bob have agreed to use the Three Pass Protocol. p=1009 Alice chooses the encryption exponent e_A = 101 Bob chooses the encryption exponent e_B = 209 Now Alice and Bob send three ...
71 views

### ChaCha20: Can my salt/pass for a KDF also be the nonce?

I have a PSK. I don't want to use it directly. I want to pass a "salt"/password into a KDF and get a new key. I need to give the other side the nonce used. I don't have enough space to fit all of ...
19 views

### Secure File Transfer with Individual Control

I am pretty much a newbie in this field, but I have been searching for an answer last 4 hours, without break. So I wanted to type it on here. My main goal is to build Raspberry Pi cloud storage and I ...
22 views

### Using PSK starting a new session, encrypt the new session key with old, or sign a derivative to be used on the old key?

I have two endpoints that go through a middleman. Both have a pre-shared and secure key, 16bytes to be used with ChaCha20-Poly1305. Extremely constrained device. No packet larger than 100 bytes total. ...
13 views

### How does a rectilinear filter used for QKD-BB84 detect both horizontal and vertical polarizations?

When using the BB84 algorithm for QKD, you arbitrarily choose which of two filters (bases) to use when detecting a photon: rectilinear or diagonal. If you choose rectilinear, you can detect ...
19 views

### How is QKD (Quantum Key Distribution) advantageous over McEliece/AES?

I don't understand the popularity of the idea of QKD (often coupled with OTP). From what I can tell, a quantum-safe key exchange algorithm like McEliece has just as much security while being able to ...
88 views

### Diffie-Hellman in Https: How are prime numbers picked?

I am trying to understand https, as I understand https uses the Diffie–Hellman method for keys exchange and then AES for encryption. But Diffie–Hellman needs two prime numbers, where do these come ...
13 views

### Does the size of data to be encrypted influence the security of Gmac?

In this link: Has GMAC mode a future outside GCM?, the last comment given by the user Demi, indicates that the larger the size of the text to be encrypted, the lower the security of the gmac. Why is ...
8 views

### XTZ Private Key

The BIP39/44 off-line tool does not contain XTZ coin. Therefore, I cannot derive (from my 24 words) my ledger nano s private key associated with my Public key for my Tezos account. Is there another ...
50 views

### Why GCM operation mode with AES-128 is recomended and can we use AES-192 and AES-256 with GCM?

It happens that on the internet I often find that AES encryption should use a 128-bit key only if it is used in conjunction with the GCM mode of operation. Why only with 128-bit keys? What happens ...
9 views

### TDES(Triple DES) DUKPT decryption

We have a POS(Ingenico) that uses DES3_CBC encryption using a derived key. It sends encrypted data, and 10 bytes size KSN. I tried to use CKM_DES3_CBC_ENCRYPT_DATA to derive the key, and decrypted the ...
22 views

### Are there any algorithms for which generating any zero-knowledge proofs is not practical?

It is related to my earlier question: Can zkSNARK or other zero-knowledge proofs be used to proof message authenticity without revealing private key? Are there any algorithms for which generating ...
15 views

### Repeatable encryption for pseudonymisation

Is there a good way to do repeatable (with the same result) encryption for pseudonymisation where the pseudonym can be decrypted? I want to set up a system to allow multiple services to communicate ...
34 views

### Security of ECC over finite fields of characteristic $p\approx2^{50\pm10}$?

What's the security of Elliptic Curve Cryptography over finite fields of word-sized characteristic $p\approx2^{50\pm10}$? We are talking about $\Bbb F_q$ where $q=p^k$ for some suitable $k$. ...
79 views

### multiplicative inverse [duplicate]

I actually do want to know how to generate the multiplication inverse (M.I) table, I mean the calculation how the M.I been generated.. such as the M.I of 22 is 5A regarding to the table.. Do you know ...
36 views

### Mathematical definition of deterministic and non-deterministic random bit generators

Can anyone give the mathematical definition of deterministic and non-deterministic random bit generator? Providing a reference will also be very helpful.
15 views

### How to find/determine the Polybius Square Key and Additive Key, if only the Cipher Text is known, in Nihilist Cipher?

I was solving a Crypto Challenge in a CTF, and I got a Nihilist Cipher Encoded String. Luckily the additive key was given as a hint, and for the polybius Square key, I kinda bruteforced or I just got ...