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10

Probability. When generating a 1024-bit RSA keypair, one of the first jobs is to pick a pair of primes p and q such that the product of those numbers (i.e. p multiplied by q) is 1024 bits in size. The simplest way to do this is to pick both values to be somewhere around 512 bits in size each, as 2512 × 2512 = 21024. Note that I'm picking 1024-bit as ...


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What the page you link to means is that there are known attacks which, when implemented, would allow building collisions with some costs: If the goal is "raw collisions" then the computational effort is equivalent to running 261 times the SHA-1 function. A raw collision is such that the attack produces two messages m and m' which are distinct but hash to ...


4

It's possible but highly unlikely: An attacker could have created a fake certificate based on compromising a CA certificate or reverse-engineering an valid one. These are both believed difficult, which is why the system is believed secure, but they have happened before. Typically, once the extent of the compromise is known, your OS or browser developers ...


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If you have messages to send, and you use an asymmetric encryption algorithm, and that algorithm happens to be able to process each message wholesale because the messages are small enough, then indeed you can design the protocol without any recourse to extra symmetric encryption. However this may lose some flexibility, and have a non-trivial performance ...


3

PKCS#8 is a flexible standard; it is a syntax for encoding private keys with optional password-based encryption. The security level that can be achieved depends on the algorithm used to convert the password into a key, and the cryptographic algorithm that works with this key. PKCS#5 defines a number of combinations of password-based key derivation and ...


3

I believe that I'm now safe from all phishing and pharming attempts. Since only few CAs can issue such "green bar" extended validation (EV) certificates you are mostly right if you trust EV certificates. It might still be possible that the CA got hacked, like done with Comodo and DigiNotar in 2011. It is not possible for an attacker to just add a new CA ...


3

SHA1 hash has 160bits. If SHA1 was safe, you would need approximately 2^80 iterations to find a collision. Why 2^80 and not 2^160? Because of birthday paradox: http://en.wikipedia.org/wiki/Birthday_attack The general "collision finding" algorithm works like this: http://en.wikipedia.org/wiki/Cycle_detection#Tortoise_and_hare ...simply, to rabbits, one is ...


2

This highly depends on the smart card. Some card simply provide a key store whereas others provide a complete infrastructure where you send your data and the smart card can sign and/or encrypt the data. The second type (which is typically meant when using the term smart card) have the advantage that the (private) keys never leave the smart card.


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The subject name, in a certificate, is in the subjectDN field, which is a Distinguished Name: a structure name whose initial goal was to serve as index in the Directory hierarchy (the Directory never existed in practice, but it can be imagined as a giant worldwide LDAP server). Sometimes, there are some usages which call for notions of identity that do not ...


2

Generally the main use for MitM at the moment is for the attacker to impersonate the website to the victim. The aim being, usually, to get hold of the victim's credentials in order to impersonate them, authenticate correctly to the website and make off with the contents of their bank account, data store, intellectual property etc. This is done, typically, ...


2

TL-DR SSL client cert doesn't need KeyUsage but if present it should be digitalSignature except for very-rare-if-ever fixed-*DH. Caveat: You tagged SSL so I assume by "path that requires a certificate" you mean SSL/TLS or something over SSL/TLS (not necessarily HTTP/S). If you mean something more like CMS or S/MIME, or XML-sig, or even PGP, the answer may ...


2

The protection is called "luck". The probability that such an event occurs are sufficiently low that it can be neglected. Provided that the RSA keys are generated properly. In 2012, some researchers made an interesting study in which they collected 11.5 millions of publicly available RSA keys (e.g. keys from SSL server certificates). They found that some ...


1

Native certificate-based authentication is available in unmodified upstream OpenSSH. It is not, however, based on x.509. First, generate your CA: ssh-keygen -f ssh-ca Next, install your CA key in .authorized_keys with a cert-authority prefix: echo "cert-authority $(<ssh-ca.pub)" >>.ssh/authorized_keys From that point, whenever a key is ...


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Basically, statistics. The chances of generating two identical private keys in an environment with good randomness are effectively nil.


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I think you're putting two encryption forms together and getting confused. First you need to look at encryption in two ways encrypting data and encrypting a tunnel. Encryption of data is done at the endpoint before the information is send over the wire. This can be done using Symmetric or Asymmetric encryption. Symmetric encryption is an exchange of the ...


1

A man-in-the-middle attack, by definition, involves impersonation. The basic idea is something like this: Alice wants to have a conversation with Bob. Mallory tricks Alice into sending the first message to him instead of Bob (exactly how can vary greatly). Mallory contacts Bob, pretending to be Alice, and passes on Alice's message. Bob replies to ...


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The answer to your question is: no. MiTM is done to steal information that the user THINKS they are sending to a legitimate site. HOW it accomplishes this usually involves "impersonating" whatever party you're trying to send your data to, and sometimes involves traffic decryption (although most of the time, decryption isn't feasible without some sort of ...


1

It depends. With some ciphers, it is possible to passively eavesdrop the communication once you have the private key. It may be done even for connections wiretapped before you obtained a copy of the private key used. However, for another class of ciphers, those providing forward secrecy (PFS), the client and server generate a new ephemeral key for the ...


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No. It's irrelevant, although it's better that they don't use weak root signatures. I think the setting may refer to the intermediate CA instead. Remember that from 01/01/2017 Microsoft will start rejecting SHA-1 signed SSL certificates, and Google will degrade the security level indicator for those sites with a certificate which is valid after 01/01/2016, ...


1

Cryptographically, the scheme you describe is not increasing your risk. From an overall security standpoint, adding the additional recipients creates more points where things can go wrong. Each of the recipients represents an additional endpoint where the message must be secured. You may trust each of the people, but can you equally trust all of their ...


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Yes. You can use OpenSSL to convert the certificate into different formats as required by the application / server. I've seen Apache / Tomcat configured a number of ways. Sometimes with a .pfx, sometimes with .pem files, and sometimes using the Java keystore. IIS typically uses .pfx files. With that being said, you want to make sure that your CA allows ...


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Yes, you can buy one certificate and use it on unlimited number of servers. However, some servers may require you to convert the certificate and the private key into an appropriate format. You may look into documentation to find the details for each program.



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