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0

AES as it stands a block cipher with 16-byte block size and 16, 24, and 32-byte key sizes. To encrypt even one bit, you need additional data. On the simple thaught, one can consider filling the rest with 0, then during decryption, there will be ambiguity. That is after the decryption, that data is 1 or 10 or 100 ... if the encrypted bit was 1 and similarly ...


4

Yes, those are the 5 Elliptic Curves groups that are currently supported for ECDHE and 5 Finite fields for DHE. If you want compliance with the TLS 1.3 standard, those are the only ones. DHE is losing its ground to the ECC version since ECC is faster. If you insist to use DHE the use a field size larger than 2048. one discussion into what curves should be ...


3

You can see the list of all supported groups at the IANA, which tracks all of the assigned code points. There are many more items than are listed, although they aren't available in TLS 1.3. In general, what you should use depends on (a) what security level you want to have, (b) what your software and hardware support, and (c) what your performance ...


7

(1) I'm curious whether the following 10 different DH Groups are the only groups that TLS 1.3 supports, Yes, in the sense that TLS 1.3 only allows groups that are explicitly declared as supported in 1.3. This currently includes not only the groups from RFC 8446, but possibly more recent RFC as well, such as Brainpool curves from RFC 8734. The TLS supported ...


2

This is simply a number pad implementation of the plain old original scytale. Using the number 5 key on the pad instead of a rod. It's a basic substitution cipher. Was the TV show the first to use the number pad in this way? I cannot answer that. I doubt it.


2

Key splitting (best case scenario) The ideal cryptographic algorithm for this purpose is Shamir's Secret Sharing, as it provides Information theoretical security, meaning it's mathematically impossible to recover the actual key without having the k number of shares specified by the person splitting the key. We don't know how many shares are needed, and/or if ...


2

When you are using private/public key authentication and agent forwarding, a full ssh mitm attack is still possible. Agent forwarding is a security issue and should not be used. In cases, when agent forwarding is not used, a full ssh mitm attack is not possible, but an attacker can redirect the traffic to another server and log your input. When you are using ...


2

Let formalize the secret in the middle as; signature = Hash( m[1..l/2] || secret || m[l/2+1..l] ) where l = len(m). This construction is not differ from the original H(k,m) since simply consider that k = m[1..l/2] || secret and then apply the length extension attack, success! The attack append-only attack H(m,k) - linked by user49075 on the comments - ...


1

A keyless entry system means just that: it allows the entry into the vehicle (by unlocking the doors) without using a key, usually using some sort of radio fob. Many vehicles also pair this fob with an anti-theft (immobilizer) system and require the fob to start the car, but they need not be the same thing. In systems with radio fobs, cryptography is ...


0

Bruce Schneier describes the process in his 1996 book, Applied Cryptography: There’s no real security here. This kind of encryption is trivial to break, even without computers [587,1475]. It will only take a few seconds with a computer. Assume the plaintext is English. Furthermore, assume the key length is any small number of bytes. Here’s how to break it: ...


0

I think Amussen mixed it while trying to make it clear. Consider that you have 264 possible 128-bit keys instead of 2128 then the possible keyspace is reduced to half of its security. This time you will ask how the attacker will know which ones are missing. Since we assume that everything is known but the key, we also know the key-space. So if we have time ...


1

Conceptually, this is possible and secure. Whether it's a valid program in particular depends deeply on the arcana of the atrocious OpenSSL API (for example, explicitly requesting the GCM tag is required when using GCM with OpenSSL, as it will cheerfully both encrypt and decrypt with no tag ever generated or input). I'm not going to say for sure that this ...


0

If Bob is never allowed to see Alice's public key, ever, then there's no way for Alice to prove to Bob that she owns A*, if Bob only has access to h(A) and h is a general-purpose hash algorithm. Bob has insufficient information. The only way to make this work is for Alice to send Bob A as part of the proof. He can then compute h(A) and compare it against his ...


1

The general idea behind such proof is that A signs some message ("challenge") created by B with its private key - and that this signature can be checked. B creates a random challenge which is then signed by A. It is important that this challenge is not predictable in order to avoid replay attacks. A then sends the signed challenge and the public ...


1

According to Raymond Chen at Microsoft, even version 4 GUIDs used in Windows since 2000 are not cryptographically secure. They use the basic random number generator, which can allow someone to predict past and future GUIDs if they know the state of the generator. Granted, this would only be relevant to a security-sensitive application. It's important to know ...


1

If I'm not mistaken, starting last June, all testing was to go through NIST's Automated Cryptographic Validation Protocol (ACVP). An overview is available here, and more information is published on GitHub. I think this provides some transparency into the process, though I'm not sure this is the kind of public/transparency you where asking about. Cheers,


2

The first issue here is how you describe the use of "public" and "private" in terms of Diffie-Hellman. In DH, you don't have a single public and private keypair. Both parties have a public and private keypair, and they both exchange their public keys with each other. From that exchange, they may both agree upon some shared secret. The ...


1

The motivation is in my opinion pretty clear from PEP 506: ... concerns that Python's standard library makes it too easy for developers to inadvertently make serious security errors ... Although the documentation for the random module explicitly states that the default is not suitable for security purposes [2], it is strongly believed that this warning may ...


3

First of all, your private key is usually encrypted, with a key derived from a passphrase (this is the passphrase you need to enter any time you want to decrypt or sign a message). The key generation from the passphrase isn't the greatest (it's an old algorithm) so you need to use a really good passphrase if you're worried about the key being stolen. You'll ...


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