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6

An existential forgery of a chosen plaintext is having the ability as an attacker to obtain a valid MAC for a plaintext of your chosing, without knowing the key required to generate a correct MAC. A common vector for this is a timing attack, and that would work like this: The attacker sends a message, and an HMAC (really just a sequences of bytes the ...


6

This really depends on the site, the level of information being stored, and the TTL (time to live) for the record. Google tends to handle a lot of different accounts for people: gmail, YouTube, blogger, Android accounts, search histories, contacts, calendars, etc; all of the stuff a spearphisher wants. Likewise their app, Google Authenticator, changes keys ...


5

It has to do with the potential for early entires masking later ones: Note that earlier entries in /etc/passwd take precedence over, or mask, later entries with the same user name or same user ID. Therefore, please note the order of the entries in the example for the daemon and sync user names (which have the same user ID). Make sure you do not alter ...


5

Are there others I am missing? The one-time password has more entropy than dog's name and is less vulnerable to enumeration/dictionary attacks. On a phishing site, it is fairly easy to display some trivial personal question (e.g. what is your dog's name). The phishing site doesn't need to know the answer. On the other hand it is pretty ...


5

Session state within an application should ideally be managed server-side from a security perspective. So in terms of expiry a list of active sessions should be stored and they should be removed from the server after an agreed period of inactivity (exactly what this would be depends on the application sensitivity, user base etc) The application should also ...


4

The EBICS financial protocol (European alternative to SwiftNet) can be a pertinent real life example. It uses three certificates respectively for authentication, signature and encryption. Most (if not all) banks use three different certificates. However the official protocol specifications allows the use of the same certificate for authentication and ...


3

Sometimes we forget what counts: The system is protecting things, you and your coworkers are a people. When kidnapped, just cooperate and try to keep harm to persons as low as possible; it's just not worth it. With this corrected attitude, it doesn't matter what security system you pick, because it will only work with the thieves, not with the robbers.


3

The user name and password are encrypted; this is confirmed in the OpenVPN documentation: OpenVPN 2.0 and later include a feature that allows the OpenVPN server to securely obtain a username and password from a connecting client, and to use that information as a basis for authenticating the client.


3

PIN numbers do not replace passwords. A password is still required. PINs allow you to have a very strong password with the convenience of being able to quickly unlock your device. PIN numbers in Windows 10 are not really included to increase the security of that specific device. In order to configure a PIN number on a device you must first log into that ...


3

This is actually a common misconception because intuitively, it seems like adding random delays should thwart timing attacks, until you think about it a bit deeper. Theoretically, if the lengths your random delays are unbounded, ie drawn from [0, infinity] then it would thwart a timing attack for the reason that you suggest. In practice you A) don't want ...


2

Theoretically, this will not work. The attacker already has randomness from the delays of the network, adding extra randomness doesn't prevent timing attacks, it just means the attacker needs more data for their analysis. Practically, it might make timing attacks infeasible because of the amount of data needed for analysis But there are better ways to ...


2

You should use a password, without any doubt. A 4-digit PIN is easily crackable via brute-force; for this reason it is only used in conjunction with other mechanisms that deny access after a limited number of tries, e.g. SIM cards and bank cards. Any other use is doomed to failure, as the hacking of Google Wallet showed a few years ago. Longer PINs are ...


2

This isn't a good idea. Using OAuth 2.0 or OAuth 2.0ish protocols for Authentication isn't correct. OAuth 2.0 was designed as an Authorization protocol. Using OAuth 2.0 as an authentication protocol carries a handful of security implications. OpenID Connect was developed to fix these deficiencies in OAuth 2.0 so OAuth 2.0 can be used for authentication. The ...


2

Diffie-Hellman and MIM attack: When variants of Diffie-Hellman algorithms like DHE, ECDHE etc. are used in SSL handshake for key exchange then can it become prone to man in middle (MIM) attack. Suppose, SSL handshake has started and now it is time of key exchange, so client computes its public key part of DH and sends it, now bad guy sitting in the ...


2

Most businesses require employees to cooperate with thieves to the best of their abilities, along with insurance to replace anything lost during a fire, theft, or natural disaster. It is hugely more expensive to repair the bad press and pay your workers compensation (or worse, pay when your spouse sues them after you die)! It's just not worth it! If you ...


1

According to these slides, during the handshake both the operator and the SIM card uses A8, RAND, and Ki to generate a session key (Kc). After the operator compares RAND_1 and RAND_2, it uses Kc to encrypt a message. The mobile then tries to decrypt the encrypted message with Kc; if this decryption is successful, then the mobile had, in effect, ...


1

And if my disk is not encrypted maybe it generally doesn't matter whether I have pwd or PIN? I don't have enough reputation to comment, so I'm writing an answer. If you are not using disk encryption it doesnt matter are you using password or PIN. If someone wants your information, he will restart your computer and put a LiveUSB with Ubuntu (for ...


1

But how RSA is used to prove the server identity or authentication because it is done with digital signature, right? Yes. The key exchange parameters are signed with the server's long term key. (Such a key used to be mostly RSA, but ECDSA is becoming quite common now.) Further reading See the Key Exchange section in Thomas Pornin's answer here: How ...


1

The problem you are trying to solve is that the client needs to be identified by the server (to know which user this is) but the server needs also be reliably identified by the client to detect phishing. I agree that simply using HTTPS for identification of the server is not enough, since an attacker might simply own a similar looking domain (e.g. paipal.com ...


1

Security measures strengthen in inverse proportion to convenience... so I probably wouldn't do this... and I don't know a single site that does this... but... you did ask. How about a workflow like this: User accesses web site and enters user name Site looks up user's phone number and sends one time code or a random word as SMS. Site displays one time ...


1

I know of one that let's users upload a picture of their own choosing when the account is set up. (They can change it later.) The picture is shown on the password screen, after the user ID is entered. Wrong or no picture == fake web site. You would want to use a back-end program to make the pics a standard size and to strip out meta data before storing ...


1

From the blog post itself they state that unlike Google Authenticator, the Authy system actually generates new, separate keys for each device. As such I don't see any reason that they would need to store them so an attacker compromising their database should not be able to access them. An attacker who compromised one of your devices would have access to a ...


1

From the docker documentation on container linking, it's possible to see that the standard setup for links is to create an internal network on the docker host which is used by the containers to talk to each other. This network isn't exposed off-host by default so from that perspective it should be secure from network based attackers (i.e. no ports or ...


1

Yes it is possible. If tokens are server generated by creating a cryptographically secure random sequence stored against the account, this token could be refreshed and reissued on a certain interval, invalidating the old one. The token would only be refreshed on active use so it won't invalidate the old one when the client computer is off. This approach ...


1

Is there a problem that two different users (with two different phone numbers) will get the same generated 4 digits code? It is not a matter of how many numbers we can generate from 4 or 6 digits (because, regarding the number of population, the number of combinations we can do with 4 or 6 digits is not significant and does not make a difference). ...


1

The one-time token offers much more security than the secret question simply because it implements 2-factor authentication; all things being equal, 2FA (password + code via SMS, password + RSA SecurID token, etc) is always safer than a simple password. On the other hand, the infamous "secret question" - so often offered by web services as a security ...


1

The use of six digits allows you to have one million available combinations. While you state "Is there a problem that two different users (with two different phone numbers) will get the same generated 4 digits code? if this is a problem, obviously 6 digits code won't resolve it" - well actually, no - a six digit code gives you more available numbers and ...


1

Can anyone help me enumerate all the reasons that the one-time token is more secure than the security questions? To assess the security of a system we need not only praise its advantages but also its drawbacks. So I am rather focusing on this last aspect as you and @JohnWu mentioned the essential positive sides of OTPs but which are vulnerable to ...


1

Is there any prior research that describes how a cookie, or cookie alternative would be used to provide such a guarantee? I don't think you can provide such a guarantee, except by perhaps saying so in your privacy policy and then following that policy. The scope would be restricted to a one, or a very limited set of URLs, Setting scope can be ...


1

I don't think this will provide any benefit. On a secure web application, the less you depend on client data, the better. I can see some issues: This will surely create a vulnerability named Session Fixation: an attacker can create a session, lure your client to a special page, and have the session data on his hands. The server has no means to know if a ...



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