e-sushi
  • Member for 8 years, 8 months
  • Last seen more than a month ago
Data I/O operations for encrypted files
Accepted answer
4 votes

Ad hoc… What you’re describing is not much different from the encryption in storage systems… only that your “storage system” is a file (foo.txt) instead of a hard drive. Now, in a perfect world you ...

View answer
Is Curve25519-java secure?
Accepted answer
4 votes

Related to Curve25519 Curve25519 seems to be secure so far. Yet, you have to remind yourself that Dr. Bernstein specified Curve25519 for key-exchange. Meaning: key-generation, transaction signing, ...

View answer
PAK Diffie-Hellman vs. sharing high-entropy key
Accepted answer
4 votes

Are there any advantages to “1.”, especially when users must communicate the password/key through a separate channel in both cases? As the comments (1, 2) already indicated: the first option “1.” ...

View answer
RSA Key and RSA Security
Accepted answer
4 votes

In both cases (the company name and the algorithm name), the letters “RSA” stand for the initials of the surnames of Ron Rivest, Adi Shamir, and Leonard Adleman… $R$ivest, $S$hamir, and $A$dleman. ...

View answer
Is ISAAC Cipher Cryptographically Secure?
Accepted answer
4 votes

It somewhat depends how you define “secure“, but as far as I know, it has not been broken yet. Potential attacks and/or weaknesses: Brute force to find 256-bit key. ~ Obvious. Paul and Preneel (2006)...

View answer
Time Capsule cryptography?
4 votes

Quoting Rivest et al: There are 2 natural approaches to implementing timed-release crypto: Use "time-lock puzzles" - computational problems that can not be solved without running a computer ...

View answer
In S/MIME, are the same certificates always used to sign and encrypt messages?
4 votes

No, clients do not have to use the same certificates for signing and encrypting messages. Actually, you already noted the reference yourself. Let me quote RFC 5751, section 2.5.3 on page 13: 2.5.3. ...

View answer
If you wrote a reversible SHA-256 algorithm, how many "metadata" bits would be required for reversability?
Accepted answer
3 votes

If you wrote a reversible SHA-256 algorithm, how many "metadata" bits would be required for reversability? If you would write such an algo, it would not be SHA-256 anymore. Also, it would lose its ...

View answer
Decrypting SHA-512
Accepted answer
3 votes

A cryptographic hash function like SHA-512 is a “one-way compression function” – so it can not simply be “decrypted” with some tool. Instead, when you are trying to “break“ a hash output like the hex ...

View answer
Is there a consensus on what text encoding to use when hashing a string?
3 votes

The consensus is: a hash generally expects binary bits as input (practically, most implementations therefore handle it using binary bytes, aka 8-bit unsigned chars in the range 0x00-0xFF) and it will ...

View answer
Writing your own Encryption algorithm?
3 votes

If you really expect it to be … 100% uncrackable… you’ll have to start by abandoning your “keep certain parts private” idea and assume that “the enemy knows the system”. See Kerckhoffs’ ...

View answer
FIPS 140-2, Level 1 validation vs. compilation
3 votes

You can convert/cross-compile the code, but that won’t port over any validation or even certification. In the end, a cross-compiled product is a new product – requiring revalidation. Unless such (re)...

View answer
Is it generally considered acceptable for app owners to be able to retrieve private keys from users when their apps offer end-to-end encryption?
Accepted answer
3 votes

Is it generally considered acceptable for app owners to be able to retrieve private keys from users when their apps offer end-to-end encryption? No, it's not acceptable if the app providing service ...

View answer
Is there a way to bruteforce the private key of this cryptocurrency altcoin?
Accepted answer
3 votes

First up: APC != APW. The later is a different fork, which you missed to follow… costing you cash. Besides that my research showed that the original APC coin site is down, 99.9% of its block explorers ...

View answer
Why is does the protocol of Ding et al. produce biased bits and does it relate to passive security?
3 votes

The usual definition of (passive) security for key exchange requires the agreed-upon key to be indistinguishable from uniformly random. That's not the case for DXL14 because the bits of the key are ...

View answer
Is it possible to attack an SHA-256 hash seeded with PHP’s mt_rand function?
3 votes

Yes, it’s possible to attack this construction for a simple reason: the code you show is insecure, because mt_rand is not cryptographically secure. Even worse: you are obviously relying on PHP’s ...

View answer
Is it possible to make time-locked encrytion algorithm?
3 votes

This answer comes a bit late, but… Yes, it possible to make a time-locked encryption algorithm. One of many places to dive a bit deeper into time-locked crypto would be the "publications" page of ...

View answer
Can/Which encryption algorithms be daisy chained to create a cryptographic computational puzzle?
3 votes

Can encryption algorithms be used daisy chained like this to create a simple computational puzzle… It can be done, but remember encryption algos are built to be (among other things) fast/speedy while ...

View answer
Can someone randomly guess the key to AES 256 bit encryption?
3 votes

Theoretically, this is possible... but, you have a better chance being hit by a meteor within the next second than seeing that happen as it practically boils down to "getting extremely lucky" with a ...

View answer
Using 32 hexadecimal digits vs ASCII equivalent 16-character password
3 votes

Strictly cryptographically speaking, both will represent the same entropy… just differently encoded. So, the strength can be assumed to be equal. The main difference between binary and hex will ...

View answer
What is logical key hierarchy (LKH)?
3 votes

Since I haven't heard of it and it isn't immediately obvious (not even from the linked RFC) what it does or how, can somebody provide a short explanation? In short, Logical Key Hierarchy – LKH – is a ...

View answer
Looking for the inverse of the following equation
Accepted answer
3 votes

You can either try to grasp what @SEJPM already commented: The given equation evaluates to false and there are no variables in there so it can never be true. Or you can look at it in an even more ...

View answer
Finding AES ciphertext stealing test vectors?
3 votes

Depends on what exactly you need. Some test vectors can be found in the document "RFC 3962 - AES Encryption for Kerberos 5". If you take a look at page 11, you'll find some test vectors for CBC with ...

View answer
What is straight line black box reduction?
3 votes

A straight-line black-box reduction is one that interacts with the adversary in a black-box manner (read: is given oracle access to the adversary) and "cannot rewind" the adversary. So, assuming (as ...

View answer
Truncated 60 bit SHA1 collision detection?
3 votes

It seems I am now running out of memory before computing the end answer which is bizarre Typical brute-force issue. Here’s a hint: do NOT store results in arrays as that’s most probably what’s ...

View answer
Does a Vigenère cipher with SHA-512 and a little foresight turn into a one-time pad? How safe can it be?
3 votes

No, that’s not a “real one-time pad”. As I explained in another answer of mine… Per definition, OTP requires the “key“ to be… a truly random one-time pad value, generated and exchanged ...

View answer
Is there any open-source white-box implementation of AES or DES?
3 votes

Adding my 2 cents, I would like to point out that many published methods for white-box cryptography have been broken. This includes… white-box AES “Cryptanalysis of White Box AES Implementation” by ...

View answer
Why is plain-hash-then-encrypt not a secure MAC?
3 votes

…something like HMAC is used rather than a plain hash. HMAC is a keyed hash… which means it additionally provides unforgeability. A “plain hash” (which I assume to include cryptographic hashes) ...

View answer
Is modern encryption needlessly complicated?
3 votes

… One-time pad is not only ridiculously simple, but also has been shown to be impossible to crack (if used appropriately). … One-time-pads may provide ideal security, but they are awfully problematic ...

View answer
How do you test the security of your cipher?
3 votes

This somewhat reminds me of “How do I test my encryption?” but that question was more specific than this one, which seems to be too broad in it’s current state. Nevertheless, there’s an easy answer ...

View answer
1 2 3
4
5
7