# All Questions

24 views

### Can we use the sponge construct to efficiently authenticate any cipher?

The sponge construct facilitates authenticated encryption independently of the function used to mix its state. Could we use any strong cipher (i.e. AES-256) as the mixing function in a sponge to ...
73 views

### Confidentiality then Integrity with different keys

Can anyone describe how we can do what is said in the below sentence which is in Mark Stamp crypto slides (PPTX) on slide number 101 : Can do a little better - about 1.5 “encryptions” The whole ...
40 views

### Is it safe to use a key as message in keyed hashing (HMAC)?

Scenario: User gives password. A "password key" is derived from the password (e.g. by PBKDF2). A random salt is applied. The password key is hashed with a HMAC algorithm (e.g. HMAC-SHA256), with ...
63 views

### Why is the compression function in Miyaguchi-Preneel scheme secure?

I was reading about the Miyaguchi-Preneel scheme and had difficulty in understanding why the compression function, $h(H,m)=E(H, H \oplus M) \oplus M \oplus H$ can be called secure. The only resource I ...
32 views

### Reykeyed AES in CTR mode as a stream cipher

Suppose one uses AES in CTR mode to generate a keystream, but every $l$ bytes the $n$ bits that would follow are used as a new AES key. Assuming that AES is a secure PRP: Is this a secure stream ...
29 views

### Does SIV mode work for asymmetric crypto?

In ECIES and similar schemes, is it possible to use a hash of the plaintext as the IV?
65 views

47 views

### Effect of the birthday bound on AES-GCM

What is the effect of the birthday bound on the security of AES-GCM, when a very large number of messages are encrypted? I am looking for attacks that are useful in obtaining information about the ...
44 views

### Can anyone tell whether this RHO step of SHA3 is correct?

In rho step of SHA3, I have done right circular rotation whether its correct ?? I am doing in Verilog so I am using concatenation operator for rotation. For x=0 and y=1 that is A[0][1] rotation will ...
44 views

### Is this a better GCM?

Using the keystream from the block cipher for both parts of the GMAC key (initialization and encrypting the auth tag) seems to produce a better mode of operation than GCM, as successful forgeries and ...
42 views

### Can an attacker recover the key if a Poly1305 collision is known?

Suppose that messages $m_1$ and $m_2 \neq m_1$, both known to the attacker, are both MAC'd through Poly1305 with the same key. By chance, these two messages hash to the same value. The attacker ...
41 views

### Weighted secret sharing scheme?

Is there a secret sharing scheme where secrets can be weighted, and that you need a total weight of $1$ to unlock the secret? I know that you could, of course, just figure out every subset that has ...
34 views

### How are the attributes of a user authenticated in attribute-based encryption?

It seems that the papers I am reading do not talk much about this point. That is how the attributes of a user are authenticated in ABE system. To my understanding, there is an attribute authority (AA)...
45 views

### Caculated time One Point Multiplication with double and method

I am using double and add method for point multiplication in affine coordinates. How we compute 1PM in double and method? Di Wang said one point multiplication consists of repeated addition and ...
18 views

### Attribute based access control and role based, online bookstore example

I am asked to answer a question that says: One online book-store wants to grand access to clients regarding their subscription. There are 3 types of subscriptions A , B and C. Customers get access ...
26 views

### How do you apply bilinear mapping to attribute based encryption?

I'm new to both bilinear mapping and ABE. I have a vague idea of how bilinear mapping works now, but I don't understand how it applies to ABE. Can someone give me an example?