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2

I think there is an additional problem/challenge with your scheme: Beside the problem of having the key pairs generated by the server, this scheme also allows for a man in the middle attack: A asks for the key of B, server answers with his own key C. Now the server can decrypt, read and encrypt again for B and send the new ciphertext to B. Neither A nor B ...


0

Generally what happens in a https connections is that client asks for SSL certificate from the SSL compliant server it is communicating with over https. Server will provide a certificate from it's key store. After client receives this certificate it validates it's credentials depending on whether hostname is same as requested has a verifiable chain of ...


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It depends on the individual malware, but normally a random symmetric key is generated on the machine (which is used to encrypt the files), which is then encrypted with an asymmetric public key embedded within the application. This encrypted key file is kept locally on the system, but it is useless unless you have the private key to recover the symmetric ...


2

the diffrence comes from the locking / nonlocking random beeing used (e.a. /dev/random and /dev/urandom) from the Manpages of ubuntu 14.04 (man random) NAME: random, urandom - kernel random number source devices SYNOPSIS : #include int ioctl(fd, RNDrequest, param); DESCRIPTION : The character special files /dev/random and /dev/urandom ...


1

Interesting topic, for me the safest is password, I use 4 different passwords for different things depending on the security required, for example for a site like this I will use something like (mexico1970) which I dont care if it gets cracked since I just post to the site and there is no credit card info or any other important info to protect, then I will ...


2

Every time you browse GMail or your bank's website using HTTPS from your laptop in a coffee shop or airport, your are broadcasting all sorts of ciphertexts to everyone who cares to listen in. It had better be safe publicly to share ciphertexts. Assuming a great many things about the strengths of the chosen ciphersuite, crypto implementations, and ...


2

This is defined in IETF RFC4945, section 6.1 (page 36). It is basically a standardised format for protecting important identifying start and ending sequences of encoded data in plain-text files, known as an encapsulation boundary, that has been around for a long time (since at least RFC934, published in 1984).


1

Yes, sharing the ciphertext is safe. Kerckhoffs' principle, which modern cryptosystems are designed around, states that the system should be secure if everything about it is known except the specific key used for encryption/decryption. Additionally, security through obscurity is rarely effective. What you're (somewhat) getting at in your question is that of ...


13

Exposure of ciphertext does not inherently decrease is security of the algorithm. However, if the ciphertext is more easily accessible it is more likely to be found by an adversary. If your adversary has means to steal your private/shared keys, rubber hose you, etc its more risky to increase exposure. You may always want to consider that in the future a ...


43

That is exactly what encryption is designed to safely enable. If Bob and Alice could safely share the message without allowing attackers and eavesdroppers access to it, they would not, in fact, need encryption at all. So, yes, it is safe to allow any and everyone access to the ciphertext. You do want to authenticate it so that it cannot be tampered with ...


0

Based on this answer from Thomas Pornin: Revocation is on per-certificate basis. What is revoked is the certificate (i.e. the binding between your key and your identity), not the key. Of course, if several CA have issued certificates that bind your key to your name, and your key gets stolen, then you would like all these certificates to be revoked. ...


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I am posting this as an answer as it is too long to get in as a comment. :) The following process described is with regards to openvpn & PKI. Client has the following files: ca.crt, client.crt, client.key Server has the following files: ca.crt, server.crt, server.key, dh2048.pem, crl.pem The process as per my understanding: Key exchange ...


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As it turns out, I asked this question in 2012, but now in 2015, there is actually an attack that makes this possible. Depending on the implementation, clients can be vulnerable to this attack which can allow an attacker, a MiTM to spoof any signed certificate that he wants. https://www.smacktls.com/ provides an in depth explanation of how this works ...


4

I would recommend using a completely separate root for the external and internal certificates, to prevent any information leak about internal hosts or users, through Root01, but also prevent any implicit trust by broken software. By using 2 separate root for external and internal use, theres no possible for any trust to leak from External to Internal ...


0

The basic protocol for getting a singed certificate from a CA is the following: Requester generates a key pair (a private key and a public key) The private key is put aside and should never leave the computer Requester generates a Certificate Signing Request (CSR) which contains basic information that will go into the final certificate (Distinguished ...


1

The change of a certificate in a web-server is not just a basic configuration setting. For example, changing a certificate for a website on apache requires a full restart. This means that the established connections will be cut off by the restart anyway. Suppose you do this fast enough, subsequent request from user that were using your website will have to ...


0

What you can do in this situation is to use hybrid cryptography, in which you encrypt the message with a symmetric algorithm and encrypt the symmetric key with the recipient's public key. You can easily adapt that to send a message to many clients, each with their own public key. What you do is encrypt the symmetric key with client A's public key, and with ...


0

No. You have to use one pair for each client! Ideally, each client have to produce it's own pair and send to you his public key with a certificate request. So you could work as a certificate authority and validate, then publish all public keys.


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If each member has its own private key, then each member must have a corresponding public key. None of these public keys can be identical. If you want to distribute data from one system to one or more other systems using encryption, please use an existing protocol to do this, like TLS or SSL, as these techniques have been tried and tested and are proven to ...


2

Trial certs There are several CAs that will generate short-lived trial certificates for you. Here's one: https://www.instantssl.com/free-ssl-certificate.html Short certs And there are some CAs that will generate longer lived free certificates for you. StartCOM/StartSSL has been doing this for several years. https://www.startssl.com/ StartCom on Wikipedia ...


1

You can use OpenSSL to generate your own personal certificate authority that you can use for testing purposes. Here is one example: http://www.dylanbeattie.net/docs/openssl_iis_ssl_howto.html


1

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox only connect to it securely. As a result, it is not possible to add an exception for this certificate.


1

I ran out of space on my previous answer, but think this is valid and useful information: Revocation The next few sections discuss CRL and certificates, but before you get too far I want to draw your attention to an issue that may affect production and PKI operations: If you think your PKI will revoke twice the same certificate with Microsoft's PKI ...


0

Key distribution possible with DNSsec You can use cert pinning to distribute a key. But only if that distribution method is authenticated itself in some way. So for example, you could store the pin in DNS and secure DNS via DNSsec. Otherwise, yeah, you're back to Trust-on-first-use. And if you're not sure that your initial operating system is secure, then ...


3

You mention mobile applications. Mobile applications are typically installed from a specific vendor-controlled app store (the App Store in the case of iOS devices and the Play Store in the case of Android devices). You have to trust the store to deliver the correct binary to the device but it's still much safer than the CA system that allows any CA to sign ...


6

First of all, although you used pgp, I assume you will actually be using GnuPG. Otherwise, fetch it - it's free software. Although PGP will probably also have similar functionality. Hidden Recipients It depends. If the sender included the recipient's key fingerprints, you can retrieve them; otherwise (if encrypted using the --hidden-recipient option) ...


1

It turns out that this is pretty interesting stuff. From the Martin Kleppmann's blog "Improving the security of your SSH private key files" (Posted 2013-06-26. Archived here. HackerNews'd here): But how do you get from the passphrase to the AES encryption key? I couldn’t find it documented anywhere, so I had to dig through the OpenSSL source to find ...



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