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How Encryption Works
It's not wrong, but it can be misleading for people who don't understand that it's how your server is set up and what your clients support that matters. Here's a screenshot of the ad: What happens to all my social networking information when I die? By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service , privacy policy and cookie policy , and that your continued use of the website is subject to these policies. Thus the security of the asymmetric algorithm is dependent entirely on how hard it is to solve for the private key given the public one. Public-key encryption takes a lot of computing, so most systems use a combination of public-key and symmetric key encryption. Once your browser requests a secure page and adds the "s" onto "http," the browser sends out the public key and the certificate, checking three things:

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At the end of the handshake, whichever of these two steps were used, the client and the server are in possession of a common pre-master secret , from which they derive a master secret see RFC Section 8. Besides the key type RSA or DSS , there is nothing in this that makes the size of the encryption key depend on the certificate. In addition, both types have cipher suites that use bit keys: DSS is a signature-only algorithm, so you wouldn't get an RSA-like key exchange to encrypt the pre-master secret.

The size of the key in the certificate only matters to prevent forgery of the key exchange or to be able to decipher recorded traffic back: This is why a sufficient large asymmetric key matters. Certification Authorities tend to put " bits" on their websites because it looks good from a marketing point of view. It's not wrong, but it can be misleading for people who don't understand that it's how your server is set up and what your clients support that matters.

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service , privacy policy and cookie policy , and that your continued use of the website is subject to these policies. Questions Tags Users Badges Unanswered. Understanding bit SSL and bit encryption. Here's a screenshot of the ad: Hope that clarifies the question. JohnJ 1 6 8. I'm looking for an overview of what the difference is. Hmm I don't get why a certificate vendor talks about bit encryption.

The symmetric encryption used by SSL is completely independent from the certificate. I agree, but maybe it is useful? Given the accepted answer below, my question is how would the client know to generate a random bit key?

If the server plays a role in the client's decision, then I can understand why the vendor would display this info. Gilles I think that question is asking more about the bit encoding of keys, whereas I believe this one is about the difference between the types of keys.

Thomas Pornin k 50 Can you clarify this part: In this case, the client is the browser? If so, does the ad mean to say that the root encryption is for the handshake portion and the bit is for the data encryption? Hope I'm getting this. Ignore that question - I get it now. I combined your answer with the one in this post: However, wouldn't the tougher algorithm imply a greater level of security?

I'm referring this part in your answer, "That said, because the algorithm is based on something that is simply really hard to figure out but is solvable , it is less secure than a symmetric algorithm based on a shared secret more on that later. JohnJ - The problem is that it is solvable. A symmetric algorithm based on a shared secret key does not publicly provide the information necessary to solve it. There are some tricks that can be used to make more educated guesses, but it does not rely on a problem being hard to solve.

If anyone ever came up with a way to factor very large primes quickly however for example, through quantum computing , RSA would immediately be broken and useless because the information shares is mathematically enough to determine the plaintext. To clarify further, RSA is the asymmetric, bit algorithm, while the symmetric is the bit portion. Most of the attacks against symmetric encryption involve looking for either a known plaintext the thing being encrypted or patterns that result due to poor key selection or a problem in the underlying algorithm, but that is all based on analysis of the cyphertext as opposed to analysis of the key itself since the key is unavailable.

The inherent weakness in asymmetric cryptography is that the public key must be related to the private key and thus the private key can be derived. Thus the security of the asymmetric algorithm is dependent entirely on how hard it is to solve for the private key given the public one.

There is no "challenge" "encrypted with private key" which is not an accurate description of signing anyway; there are dozens of questions about that. For DHE and ECDHE key exchanges as described by Bruno, but not pure-RSA you and Thomas describe, the server adds a signature to the ServerKeyExchange message, whose contents are neither chosen nor echoed by the client, and which is after the server cert really chain is sent and presumably validated.

Just to add some details to the existing answers When two computers initiate a secure session, one computer creates a symmetric key and sends it to the other computer using public-key encryption. The two computers can then communicate using symmetric-key encryption. Once the session is finished, each computer discards the symmetric key used for that session. Any additional sessions require that a new symmetric key be created, and the process is repeated. How will biometrics affect our privacy?

What is a digital signature? How Fingerprint Scanners Work. Look for the "s" after "http" in the address whenever you are about to enter sensitive information, such as a credit-card number, into a form on a Web site. The padlock symbol lets you know that you are using encryption.

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