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You can't have two different public keys for the same RSA private key. That's just not how RSA works. Well, almost. There's a minor technical loophole, and it's the fact that RSA has equivalent keys. In particular, the public keys $(n, e)$ and $(n, e + \lambda(n))$ are equivalent, in the sense of producing the same ciphertext for the same (padded) ...


4

Do (should) services where the customer has to provide a public key, check this public key for weaknesses? What kind of weaknesses could a key be tested for? I'm pretty sure that there's no easy way to find out if a public key has been generated safely without some sort of brute-force attack. Ultimately I think it's up to the creator of the public key ...


3

Although PKCS1's ASN.1 is a quite common representation of RSA keys, it is not the only one used (and certainly not the only one possible). The standards for XML digital signature and encryption unsurprisingly use XML not ASN.1 for data structure: https://www.w3.org/TR/xmldsig-core1/#sec-RSAKeyValue The standards for JSON Web Signature and Encryption (...


3

Logjam is a two-step process. First, you take a group and apply a precomputation to it. Most people use one of a few different groups, so breaking a single group effectively breaks every single key exchange done by anyone using that group. If a group is "broken", then any key exchange done with Diffie-Hellman using that group can be broken quite easily, ...


3

As pointed out in the comments, this allows for a small and negligible number of weak keys which can be avoided. Let us not forget that this pioneering paper was published before any examples of public key cryptosystems were known in the open literature. The authors took the astute position that if good cryptosystems were discovered, a few weak keys should ...


2

Also Can it be prevented If I store the Public key in a certificate store? Well, an adversary could probably just overwrite that entry and mount the same attack as before. Now I have a problem, what if someone's signs the license file content with entirely new set of private\public key pair. What you have stumbled across is the "trust problem" of public ...


2

The term ‘perfect forward secrecy’ is bad. Rather than talking about whether a protocol has perfect forward secrecy, you should talk about when in the protocol you erase keys. Then, although ‘key freshness’ isn't a common technical term in cryptography, this suggests a clear answer: Key freshness is presumably about when you generate new keys so that ...


2

How do we pick a group size for a 128-bit security level? Estimate the cost of mounting an attack as a function of the group size. Find the group size that puts that cost estimate above $2^{128}$. In this case, for appropriately selected groups, without back doors, like the RFC 3526 groups, the best attack algorithm is the general number field sieve, GNFS. ...


1

In short If the scheme is at least CPA-secure, then it is safe to encrypt and send the same message to different parts as you described. Long answer In the CPA-security game, the attacker has the ability of encrypting a $poly(\lambda)$ messages, which may even be the same message, and then it is still hard to distinguish two ciphertexts. Therefore, an ...


1

There's a wide gap between plaintext recovery and key recovery. Of course, what is of interest to users is the confidenitality of their plaintext, but if an attacker can merely recover a single plaintext (which might happen outside the domain of crypto if the user just leaves it on the tube on their way to work!), that doesn't mean they can recover the next ...


1

How large can RSA and DLOG keys be before the standard gives up? In theory, they can be indefinitely long using some implementation adaptions. However, they would become too impractical compared to post-quantum algorithms which do not require such key lengths that no one will use them. Is it reasonable to assume $10^9$ bit keys are possible with next ...


1

Is Public key used directly to encrypt a message or it is used to derive other keys? A public key is used to encrypt a message. Example: If Alice wants to send a message to Bob she would take Bob's public key and encrypt the message and send the encrypted message to Bob. A key to derive other keys is done with a Key derivation function and this key is ...


1

To understand how nonces and timestamps are used to prevent a replay attack, you must understand generally what a replay attack is. A replay attack is a network attack in which a data transmission (that is valid) is repeated or delayed. An attack like this is usually done by an adversary who happens to intercept this data and re-transmits it. If Alice (...


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Is it possible to use any method for such a large list of compressed public keys in order to finally find at least one private key? Actually, for ECC, it turns out that the problem 'given this long list of public keys, find any one private key' is no easier than 'given this public key, find the private key' The proof is the converse; suppose we had a way, ...


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I spent about 400 hours in paint to make an illustration of this, hope it helps!


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