# All Questions

4 views

### What does “Use of SHA-256 in cryptography” mean?

I am beginner to Cryptography. And recently I came across the term "use of SHA-256 in cryptography". What does "Use of SHA-256 in cryptography" mean ? Does it indicates it's use in Diffie Hellman Key ...
8 views

### Weil pairing implementation - low level programming language

I'm just started to studying elliptic curve cryptosystems. My one month-goal is to write a simple signature system based on the Weil-pairing. Some parts of it can be written without deeper ...
23 views

### Is this Pseudo Random Function (PRF): F(k,x) = f(k,x) - f(k,x-1)

I have a question about Pseudo Random Function. Let $f:\{0,1\}^n×\{0,1\}^n → \{0,1\}^n$ be a secure PRF. $F(k,x) = f(k,x) - f(k,x-1)$ is a secure PRF?
10 views

### Why should a signature use PSS padding in RSA?

Suppose I send a message using AES (private keys already negotiated securely) and I send a hash of this message using RSA (encrypted with private key) with OAEP to verify the authenticity and ...
32 views

### Will non-ECC algorithms like RSA eventually become too inefficient?

The strength of symmetric and asymmetric encryption schemes scales with the key length, but there is a difference between symmetric algorithms like AES and asymmetric algorithms like RSA. For ...
21 views

### difference between algorithms like Blowfish and AES 256bit comparisons between them? difference in efficiency between different encryption methods? [on hold]

i am doing a project about encryption, and it would be awsome if i got some help with theese questions. What difference is there between encryption algorithms like Blowfish and AES 256bit and what are ...
12 views

### what is the key and IV size in CBC encryption and Decryption [on hold]

In my question what is the key size and key size must be fixed and what is the size of IV in CBC encryption and decryption. I already tried with out IV. But the key size and IV size don't know.
66 views

### Is it overkill to run a key generated by OpenSSL through pbkdf2?

I'm generating a key & iv with OpenSSL via: ...
24 views

### Which hardware-accelerated AES-GCM implementations support encryption in-place?

By encrypt in place I mean the following. Suppose I have an input plaintext of length L and I have also allocated an extra E bytes at the start and/or end of the buffer, with E << L. So the ...
22 views

### Key expiration policy for 3DES / TDES / Triple DES

I have a system that signs plain text messages using a message authentication code (MAC) encrypted with Triple DES. The short message is used on connection to establish a session key, so it would take ...
24 views

### Use same PGP key for private and business mail addresses

I'm asking myself which one is better: Use the same PGP keypair for use with both private email addresses and business email addreses Use two seperate PGP keypairs, one for private and one for ...
48 views

### Authenticated encryption without padding

I want to encrypt data and protect its integrity and confidentiality. However, I cannot increase the length of the data. Are there any cipher modes of operation which provide confidentiality and ...
40 views

### How to calculate the maximum output size for data encrypted with a RSA Private Key?

I have an an encryption algorithm I am working with that looks like this: prv_key_enc(sha1_hash(data)) Where, the RSA parameters are: RSA/ECB/PKCS1Padding 1024 ...
59 views

### Is MITM possible after key exchange phase done successfully in RSA?

Is MITM attack theoretically possible after public/private key pair exchange is done successfully. Say Alice and Bob have genuine public keys of each other. Is MITM possible further during ...
155 views

### why inverse in diffie-hellman protocol will not give same value?

Security of diffie hellman protocol is $K=g^{ab}$.if sender want to calculate value of $b$(given $a$) he can do $g^{{{ab}^b}^{-1}}$(where K=$g^{ab}$) which will give $g^{a}$ as we are cancelling value ...
13 views

### Random numbers for Master Key and Key_block

Exploration through RFCs concludes that random numbers used in the creation of Master Key and Key Block(Key material for Encryption Key and Mac Secret) are from ServerHello.random and ...
43 views

### Secure Broadcast Channel

I've read a paper that says that one of the "assumptions" that it makes is secure broadcast. Why is this an assumption? Can't a broadcast channel be built with simple primitives--i.e. encrypt and sign ...
39 views

### SHA-256 Wrong registers

I have a problem with my sha256 java implementation. The registers (a…h) are correct until j=24; ...
79 views

### Why is “multiplying” $g^x$ and $g^y$ not possible?

The computational Diffie-Hellman problem states that for a cyclic group $G$ of order $p$ and a generator $g$, it is hard to find the value $g^{xy}$ given only $g^x$ and $g^y$ (but easy if either $x$ ...
62 views

### Unpredictability vs randomness

I'm experimenting with creating an entropy source for an environment where I have no hardware available and the language is very high level (executed in a virtual machine). I know it's not a good idea ...
114 views

### What key exchange protocols give Forward-Secrecy resisting future progress?

I (wrongly) understood what I've been told as meaning DHE in TLS, PFS in IPSec do not provide Forward-Secrecy; and I'm told that common forward-secure key exchange protocols are restricted to ...
70 views

36 views

...
52 views

### Question on BPP and NP (polynomial time) [on hold]

Informally, BPP is the class of languages that can be decided by a probabilistic algorithm in polynomial time with an arrow probability of most 1/3 on any instance. More formally, a language L is in ...