# All Questions

137 views

### SPI security of FE1 scheme

I have a question about security of FE1(Page 16-18) in paper "format preserving encryption". Can anyone explain me, why we are allowed to replace PRF with random function in security proof? And also, ...
288 views

### SHA-256 exhaustive search

How do I calculate the number of computations needed to break SHA256 in case we are using it for safely storing passwords (together with a salt)? Are there any formulas that can be employed? For ...
24 views

### Could a crypto system that uses non-FIPS crypto but then upgrades complete to FIPS be FIPS certified?

I know most people around here (including myself) are anti-FIPS, but I have a FIPS related question. Could a crypto system that is not FIPS, e.g. one based on primitives like Curve25519, achieve FIPS ...
76 views

### Calculating Multiplicative Inverse for Rijndael S-box using EEA

I am currently learning, and I'm stuck on something that I thought is very simple. On many academic sources they suggest using Extended Euclidean Algorithm to calculate the multiplicative inverse for ...
54 views

### How much pre-hashing a password increase security against brute force attack?

I am wondering how much hashing a password used as key for a symmetric key algorithm helps preventing brute force attack on crypted text. Let's assume I want to crypt text A using key B using ...
74 views

### Which is the most secure steganography technique? [closed]

Just like we have AES in crypotography, which is the most secure technique in Steganography? I am looking for a technique in which the standard image characteristic modifications it does go ...
49 views

### Can I reduce the MAC size in TLS?

The MAC size is reduced to 80 bits in truncated_hmac extension , which says "forging of MAC values cannot be done off-line: in TLS, a single failed MAC guess will cause the immediate termination of ...
36 views

### Software interface for KDF and PBKDF?

I'm working on an implementation of Krawczyk and Eronen HKDF from RFC 5869. From Krawczyk's original paper, he identifies four inputs to a KDF in Cryptographic Extraction and Key Derivation: The HKDF ...
68 views

### In what cases will RSA not work? [duplicate]

I know that there are cases when RSA will not work like when the number to feed into the system is greater than the modulus. I was wondering if there were any other cases when RSA won't work I looked ...
34 views

### How to choose McEliece's parameters?

At the time of this writing, there are 3 sources for parameters for the McEliece public-key cryptosystem out there. The first paper is the original McEliece paper ("A Public-Key Cryptosystem based on ...
38 views

### Question on Miller's algorithm (change the input m)

From the book titled " An Introduction to Mathematical Cryptography" (Chapter 5,page 322), we know that the miller's algorithm returns a function $f_P$ whose divisor satisfies div(f_P) ...
77 views

### What are the advantages of using OFB (Output Feedback Mode)? [closed]

I have a problem with OFB mode, because I have heard that it is stronger than CFB.
55 views

### Question about keyed hash functions

Maybe the answer to my question is obvious, but I have doubt... I have noticed that hash functions are studied in two forms, keyed hash functions or unkeyed. In general, lecture notes present hash ...
71 views

### Parallel authentication of encrypted data. What AE type to choose?

I've got a system with a slow data transfer channel. Transferring a message through several channels does increase the transfer speed significatnly. AES-CBC+HMAC is good except that verifying the MAC ...
35 views

### Meaning of pseudocode “$(C, S):=$”

I've seen pseudocode of this form in the Montgomery Multiplication related theses: $(C, S) := a[j]*b[0]+C$. What's the meaning of "$(C, S):=$", or what is the real code that converted from this ...
41 views

### Does anyone still use BAN or GNY logic in practice?

I want to implement a simple protocol, and I'd like to verify it through BAN or GNY logic. I would assume that if these logics are still used that there would be some programs available that would ...
80 views

### Reasons for components of AES

I started reading "Cryptography: theory and practice" by Stinson, and I am trying to understand the reason behind the choices for the different components of AES since they seem quite arbitrary. In ...
74 views

### Working on subgroup of $\mathbb{Z}^*_p$ in practice

It is said that, given a group $\mathbb{Z}^*_p$, we can always have a subgroup whose order is prime. To this end, for a safe prime $p=2q+1$, compute $x_i^2 \bmod p$ for all $x_i \in \mathbb{Z}^*_p$. ...
109 views

### Is there any practical attack to create a printable chosen prefix MD5 collision?

I would like to create two ASCII text messages with the same MD5. Is this possible? If not, is there a similar but less strict attack that could work? Or to rephrase my last question: what are the ...
125 views

### Easy explanation of “IND-” security notions?

There are many schemes that can advertise themselves with certain security notions, usually IND-CPA or IND-CCA2, for example plain ElGamal has IND-CPA security but doesn't provide IND-CCA security. ...
44 views

### Does XTS provide random write access?

I'm trying to find a sufficient encryption mode that supports random read and write access. It seems like XTS is a perfect fit, since in my use case authentication and integrity insurance are handled ...
66 views

### Using password-based encryption as a hashing scheme

Classic scheme: Given password and hashing algorithm Generate salt Calculate ...
71 views