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49

The SIM card contains a private key or more commonly a symmetric key called the "Ki", and the card is designed to never divulge this key to the outside world. The SIM card itself has physical security measures to make reading the key from the card very difficult without destroying the original card and/or the data stored in the card. For a long time, this ...


12

If you use the same password for several distinct sites, then you are doing something wrong. Each password shall be site-specific. Therefore, there shall be no reason why the "weaker standards" would have any impact on "all your passwords". (Similarly, there is no rational reason for changing all your passwords on a regular basis. There is a widespread ...


6

Explanations for weak password rules Well, those are obviously bad rules. But here are some possible explanations (or "explanations") for it: Must not start with a number The site owner might actually think that this is a good rule. To prevent for example 1234546 or just prepending a common phrase with '1' (e.g. 1password) Must not have a special ...


5

What matters is the respective abilities of Alice and Bob with regards to storage. In your case, you assume that neither Alice or Bob has any memory; they share a secret value (for HMAC), but they have not read-write slot to update. On the other hand, you also assume that Alice and Bob have clocks which are reasonably accurate (within a few minutes of each ...


5

The danger is expressed in Schneier's law: any person can invent a security system so clever that he or she can't imagine a way of breaking it. The only way anyone knows to test if any given system is secure is to have lots and lots of clever people try to break it over a long period of time. You won't have that with a system you rolled yourself.


5

The notion of "two factor authentication" is not a strictly defined mathematical notion. However, usually, it relates to having two factors for authentication. The second term is important: you are trying to authenticate a user, i.e. to make sure that the user is indeed at the other end of the line. Right now. When looking up the account membership in the ...


4

User ID are not nominally secret values; that's why we call them "user ID" and not "passwords", and why graphical interfaces for entering them don't hide the characters". However, creative designers sometimes imagine that user ID are some kind of secret, which leads to situations like what you witness: a site that tries to enforce on the user ID some ...


4

You should ensure that your session token is random and at least 128 bits. Aside from that you just basically send a session token and a user id. To be fair, only your session token should be needed to identify a user since it is unique. Ensure also that you destroy the session token after the user logs out. Aside from that it seems similar to any other ...


3

You're overcomplicating the solution, and not really gaining much out of it. Others have gone over the flaws with your implementation, but I'll outline a better approach. When a user chooses to have their authentication remembered across browser sessions, use a CSPRNG to generate a random 128-bit string. Send them this string, then hash it (SHA-2/256 is ...


3

When only the server sends a certificate, but not the client, the SSL connection is fine and dandy, but the server has no clue about who it is talking too. What SSL provides in that case is that the server can be sure that it talks to the same client all along, with no possible eavesdropper in the middle. If the server must still know who the client may be, ...


3

One reason for enforcing weaker passwords is that a weaker password is easier to remember for the user. When the user forgets their password, an automatic password retrieval procedure must be used. Such a procedure usually entails that a plaintext password is sent to an email account. This offers a lot of attack surface which is outside of the control of the ...


3

The idea behind an OTP is that it can only ever be used once, hence "One Time Pin". If you reuse the same OTP for a certain time period you are not using it only once. The single use is to ensure that a lost of compromised OTP becomes ineffective as soon as a new one is requested. If your "OTP" that is valid for a certain time period (2 hours in your ...


3

I don't think this is a security question. But anyway I think your person lied to you. Everyone knows the voice telling something like The person you have called is temporary not available. If a cellphone has no contact to the network or is switched of or the sim is not in the cellphone you get either this message or the mailbox.


3

Protections are in place to combat risks. If the risks are low, then the protections can be low. Think about a forum site. There might be no reason for the site to use "strong protection", because all you really want to do is to be able to identify who is contributing. It could be determined that the site needs very weak protections in that case. The ...


3

Create a cryptographically secure random token and associate it with the user id in your DB Perform an HMAC on the token the cookie value will then be token+HMAC This way an attacker would have to know your HMAC key in order to brute force the token and that is not possible. For validating the cookie you first extract the HMAC, validate the authenticity ...


2

(I worked for Google's Account team, specializing in Usable Security issues just like this one.) In authentication, there are three basic factors: "has a", "knows a", or "is a". The two systems under discussion are both "has a". In the case of LastPass, the user has a piece of paper. In the case of GAuthenticator, the user has a particular smartphone. As ...


2

Say, you're user "bob". You log in with your password on 2014-07-30H12:00:00 and the server, using your scheme, sets your cookie token to: enc("bob", K)+enc("2014-07-30H12:00:00", K) However, bob is malicious. While his boss Alice is away from her desk, he checks her browser cookies and finds out her token: enc("alice", K)+enc("2014-07-30H13:00:00", K) ...


2

The answer is no. The server replies with a unique identifier for the login This step in itself contains a flaw. A MITM can simply intercept this response, change the unique identifier and observe how the client sends the encrypted identifier + the username. If the attacker has pre-computed rainbow tables for whichever unique identifier is injected, ...


2

Use certificates. That way the client never shares it's private key with anyone including the server. The server just has the clients public key which isn't secret. Alternatively run a federated identity solution or leverage one such as Google or Facebook's. There are open source options for this (such as http://en.m.wikipedia.org/wiki/OpenAM ) You also ...


2

It sounds like you want public-key cryptography similar to what SSH supports. The basic idea is that the user provides their public key to the server during the account creation process, then proves their ownership of the corresponding private key during the login process. The public key, as the name implies, isn't even remotely secret, so it meets ...


2

There is no reason this cannot be done technically, and I see the occasional site doing it. But it would require extra code to be built, so it's cheaper to let you handle the login ;-) The same thing happens with the confirmation link when registering: in most cases you still have to login (but in this case there are relatively more sites that auto-login, ...


2

Just because a UUID is highly likely to be unique doesn't mean that it's difficult to guess. Version 4 UUIDs contain 122 random bits, and I would recommend that or version 5 (SHA-1). Honestly, I usually use SHA256 or higher and a long string of concatenated random numbers. Then store the hashcode in both the database and a cookie. There isn't much benefit ...


2

This really depends on the system. Simple key fobs don't do identification -- your identity is simply "someone who is authorized to open the door". More sophisticated systems will have your identity programmed into the card or fob, so that both identity and authentication are established during the unlocking process.


2

Pre-Snowden, I would have dismissed this question as being in the "tinfoil hat" category. Unfortunately, the NSA's pervasive misconduct (not to mention that of its "Five Eyes" junior partners, e.g. GCHQ, CSIS, and whatever the Australian and N.Z spook agencies are calling themselves these days), does indeed raise a troubling question. The specific ...


2

https login iframes are secure from passive eavesdropping but won't help against active MITM. The js vulnerabilities may have been closed, but the issue remains, as the parent html (served over http) can still be modified, including the url of the iframe. Then the MITM can set up the login page via http and that will be loaded by targeted users. Only users ...


2

What you are describing sounds a bit like the Apple student discount. In order to purchase something with a student discount you have to log in from your university network. Edit: The reason for them to do this is that they do not want this to be available for everyone (captain obvious to the rescue). I think they used the university network to identify ...


2

I have read your clarification. You might find a compelling argument in the following paper: In general, where the party who is in a position to protect a system is not the party who would suffer the results of security failure, then problems may be expected. [1] I.e. the "there is no need to invest in security for us"-argument. You might even pull ...


2

If you are 100% certain you can, with 100% confidence identify your wife based on her biometric data and that there is a 0% percent chance of someone spoofing her biometric data, then there will be no benefit to using multi-factor authentication. The problem comes in when the identifier, be it biometric data or username and password, can be leaked or ...


1

The main concern I would have with your proposed method of generating card grid data is whether the resulting grid numbers are sufficiently random. Since you are running randomly generated data through a HMAC (which should be fine) but then also a "mathematical formula" it is possible that could bias the resulting numbers. If an attacker knows that certain ...


1

You seem to be engineering a lot of unnecessary complexity in...unless I've missed something. If you have 64 cells generate a 64 character sequence of crypto random digits and store it. Print your card from this. And check responses to challenges against it. It's really very similar to having a 64 character password and asking for a few characters from ...



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