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1

Assuming that there is no time delay between compromising the private key and revoking the public key and that there is a way to reliably find out when the key has been revoked, this could work if you time-stamp the signature, not the file. This way, it can be shown that the signature was made before you lost your private key. However, typical key ...


-1

Is not the solution to encrypt with the recipient's public key? Anybody could have written it but only the intended receiver can read it.


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For the European Union, there seems to be a list of Trusted CA available here usable to authentify such signature. You should import the list into you software (the same way that browsers are provided with a common Web CA list already imported in them) then it will be usable as root to ensure digital signature authenticity. Some countries also propose ...


1

Does any nation-state CA (certificate authority) have a public API to verify digital signatures? No, the CAs do not verify digital signatures, the relying-parties (the recipients) do the verification by themselves, using their own software applications. Eg, use Adobe Reader (free version) to verify digitally signed PDFs. However, the CA's do publish a ...


1

You could just simply cygwin and run the commands exactly as they appear in the tutorial. You can then follow these steps to get it to run on virtualbox, for example.


3

The verification steps assume that you are already using Linux. As you're using Windows, you'll need to follow the manual verification steps from the Kali download page. To run a SHA1 checksum on Windows, download and install Microsoft's checksum app. Per this page, run it with the command: fciv.exe -sha1 kali-linux-1.1.0-amd64.iso Then compare the ...


-2

The begueradj answered your question, but you say you are getting an error, still. $ is not a part of the command line, as your error message says. Type the command without it. - begueradj's answer Try install wget using one of these commands: apt-get install wget Or: If you have aptitude then use: aptitude install wget Oooor if you don't have ...


1

For Shamir's secret sharing, the only possible method for validating a share is rebuilding the shared secret with enough shares, and see if the result makes sense. There cannot be any other method that does not involve sufficiently many shares to reach the threshold, because that would contradict information theoretic security of the scheme (basically, if ...


0

I'd say most of your arguments are valid. Typically certs used for signing have different key usage, for example "non repudiation". Many legal requirements (in various countries for example in EU) exists for digital signatures, if they shall be valid in court etc. These requirements do no exist on authentication certificates. All what you state as ...


4

There a few reasons for using different keys for signing and authentication: When using two keys associated certificates can be issued from different CAs with allows web sites to ask user only for authentication certificate on login. The certificates can be issued with different key usage - authentication one don't need non-repudiation, and signature one ...


1

A digital signature is a technological mechanism by which you can do several things, one of them being proving your identity to another entity: this is an authentication protocol. Your identity is a property inherent to, say, yourself; the notion of "electronic identity" really means "something which designates your identity and is amenable to an ...


2

Certificates are transient in nature: they expire, and must be renewed. Even worse, the validity of a certificate is the property of the current time, since certificates may be revoked at any time. Therefore, if you want to store signed documents, and be able to validate them at a later date, then you need time stamps. See this answer for some details. ...


0

It seems as though they will last until the expiration of the certificates (as in, past the shutdown of the CA) Quoting from this reddit thread IIRC, If the certs are not in a CRL, they should work until their expiration date regardless of if the CA is online. The CA will continue to function after being p2v'ed so long as the server name doesn't ...


4

You are essentially correct in your last paragraph: Is the sole purpose for authentication purposes so that one who has a public key knows that this piece of encrypted hash information is signed by the person that issues this public key (has the private key) since he/she is able to decrypt it. Though, as mentioned in comments, and in various places ...


3

q1) Correct. Every message needs to be sent with its own signature. But if lots of information has to be sent this way, it is not very efficient because public key cryptography is rather slow. Usually the two parties would rather use a protocol allowing to share a secret, then use symmetric-key authentication, like a message authentication code (MAC). q2) ...


3

Why do apps encourage you to use separate key-pairs for encryption and for signing? You are correct that there is no technical reason why you can't use one RSA key-pair for both encryption/decryption and signing/verification. But just because the technology will allow it, does not mean it's a good idea. The reason why has to do with backups and what happens ...


6

Please don't use the "explanation" of signatures as "encryption with the private key" because it is a flawed analogy that does not actually work. RSA is really two algorithms, one for asymmetric encryption, and one for signatures. It so happens that the two algorithms have some common mathematical elements, and, in particular, use the same kind of key ...


1

The classical DHE is computationally expensive, at least as these things go. This rarely matters (a normal PC can still do hundreds of DHE per second), but if you are in a situation where computing budget is tight (e.g. small embedded systems) then ECDHE is substantially cheaper. With "normal" implementations, the cost of DHE is proportional to p2r, where p ...


2

In order to have high encryption strength, one would use large DH params (16k perhaps) since the classical DHE key exchange is not computationally expensive, I can't give you hard numbers for the speed. The openssl speed command does not seem to offer the benchmark for regular (finite field) Diffie-Hellman. This answer offers guidance on practical ...


0

If you want compact signatures you should look at ECDSA. RSA is pretty much horrible if key & signature size is important. I have no idea what key strength a 256 bit RSA key would have but even 1,024 bit key is only has 80 bit strength and it takes a 15,360 bit key to achieve 256 bit strength. The raw ECDSA signatures are 2x the key length as r & ...



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