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7

A man-in-the-middle attack is a simultaneous double impersonation: Charlie poses as Alice when he talks to Bob, as Bob when he talks to Alice. Since both conversations are simultaneous, Charlie can elect to pass chunks of data from Alice directly to Bob and vice-versa, adding his own parts selectively. If Alice and Bob have a shared secret K, which Charlie ...


7

CRAM-MD5 requires that the server knows the actual password, not just some image of the password by a hash function. So if the server has to support HMAC-MD5, it has to store the password in plaintext. (The server can encrypt the password, but since it also has to know the encryption key, that doesn't help.) CRAM-MD5 was designed to avoid having the ...


6

Simple forward deniability is easy to achieve with PGP: simply don't sign the email you send ! Anybody can send emails with arbitrary contents and alleged sender; signatures are meant specifically to cancel forward deniability. However, if you do not sign you also lose integrity. What you would like is to be able to send an email such that: the recipient ...


6

This is not terribly different than what OAuth is designed to do, if we were to tweak the workflow. If you were to implement this using OAuth, your application would include an OAuth provider, and the third party would sign up to be an OAuth client. The user, who is the resource owner, when redirected to the third-party site would simply authorize ...


5

Note: according to comments, this protocol doesn't use UDP. But i'll leave the answer here as it might be useful to someone else. From your language it sounds like you're using UDP instead of TCP. Perhaps you're not, but you didn't specify. And if you are, then here's something to think about. This is especially significant if the packet boundaries are not ...


5

Assuming that the LDAPS server does not have security holes, exposing it to the wide Internet should be no more risky (and no less) than exposing a HTTPS Web server. With LDAPS (SSL outside, traditionally on port 636, LDAP protocol in it), the authentication requested by the server will be performed under the protection of SSL, so that's fine (provided that ...


5

By definition, if it doesn't matter if someone has access to or modifies your data, then it isn't sensitive and doesn't have to be secure. For things that have to be secure, then it is ill advised to use a custom protocol unless you can invest the huge amounts of time and resources necessary to ensure its security (millions). Note that there is also a ...


4

There are three relevant weaknesses in this case: Improper password storage: If your provider's database is compromised, your password is directly exposed. Although some implementations of CRAM-MD5 don't store passwords in plaintext, the hashed password is still unsalted. So far, there's no known implementation that salts the password (the salt needs to be ...


4

Most of the problems outlined by Mr Snowden are essentially side-channel attacks. The algorithms aren't suddenly less robust but rather the software and infrastructure that uses these algorithms. Root CAs for example have always been open to the nation they reside in, the protection they provide is against other normal civilians, not government agencies. ...


4

The bootstrap process is achieved when people do use the new algorithm. To gain trust in the algorithm's strength, it must have exposure. Exposure is achieved through either formal competitions like for AES, or, more recently, for SHA-3; or it is achieved through the algorithm being widely deployed and becoming an interesting target. Open competitions are ...


4

I would not say it is common to expose LDAP services to the internett. What business case do you have to do this? Is is much like you do not want to expose your database server to the Internett. It is usually access only via. DMZ services, while your LDAP rests on the internal network. If I do Shodan search for port:389 I get no results, compared to MySQL ...


4

Several cloud vendors require LDAP access to AD in order to authenticate users... I can name 10 off the top of my head; so it's not uncommon in a limited scope. I would say it is unwise to open up LDAP to the broad internet (no IP filter) without additional controls (VPN, authentication,etc) Since you're exposing your LDAP server to additional load, I ...


4

Diffie-Hellman allows two parties to generate a secret key which cannot be recovered by someone snooping on the communication. This secret key can be used to set up a secure channel between the two parties that ran the DH protocol. The secret key is established between the two parties that exchanged the initial messages. If you send out one message and ...


4

I suspect you answered your own question already. The mere fact that you want to protect the data implies that it is sensitive and should not be modified or leaked. If this is not the case, why bother with protecting at all? If the opposite is true (the data should be protected) then the "rule" stands that the use of custom protocols and encryption ...


4

You have to make a distinction between the applicative protocol and the transport protocol. SSL/TLS is a transport protocol: it ensures some security-related guarantees (confidentiality, integrity, some authentication) for a a bidirectional stream of bytes. What these bytes mean is what the "applicative protocol" defines. E.g. in HTTPS, HTTP is the ...


3

Very interesting Technology Indeed If the technology is designed, developed and safely, then it can be fairly secure. It seems to provide a lot of cool features. Configure keys to access house centrally on "App". Deploy "Key" to person as needed and for agreed timeframes and without physical delivery. Decommissioning keys as needed. Many keys possible, ...


3

I can't understand what your requirements are -- strangely, you don't seem to have listed the security requirements, or threat model, or what you are trying to achieve -- but the obvious approach would be to use a Kerberos-like (Needham-Schroeder-style) protocol. Those schemes give S a way to help A and B establish a secure channel between them. They can be ...


3

This protocol seems to be badly broken. I assume it's some sort of homework? Consider: by communicating with Bob over an insecure channel, Alice gives to Eve (the eavesdropper) the value of <R XOR K>. Then Bob, by the same token, gives Eve the value of R. What do you think can Eve do now that she has both R and <R XOR K>?


3

Firstly, it's not necessary to use plaintext: Looking at the HMAC-MD5 implementation in psuedocode: you can at least store a modified version of the password: if (length(key) > blocksize) then key = hash(key) // keys longer than blocksize are shortened end if if (length(key) < blocksize) then key = key ∥ [0x00 * ...


3

It gives no protection against MITM since an attacker could forward the challenge to the client. Requiring plaintext password storage is bad and the exchange can have have a dictionary attack run against it. You are justified in being worried about this scheme and I'd personally suggest using a different e-mail provider.


3

Your principles are correct, but the particulars can be a devil to set right. Indeed, the general schema is that: The client needs to validate the certificate from the server, i.e. verify that the certificate has been issued (signed) by a trusted CA, and that the alleged server certificate contains the name of the server. Similarly, the server needs to ...


3

Often I've used the created timestamp as a way of proving uniqueness. The general assumption is that the granularity of the timestamp will be unique enough that a given receiver can assume that only one request with the timestamp or with a unique value that includes the timestamp will be received. That would prevent some forms of replay attack, where an ...


3

Enable all of the versions that can be enabled (preferably, TLS 1.0 and higher), and then let the order of preference to the server. Since you're using Internet Explorer, go to the Internet advanced settings and enable the following according to your version: Internet Explorer 6: Enable TLS 1.0 Internet Explorer 7: Nothing to do. TLS 1.0 is enabled by ...


3

As usual, the problem is one of definition. Namely, what makes the device 'D' more "genuine" than a PC run by some ill-intentioned individual ? If you get down to it, you will say something like: device D is genuine because that's the true piece of tangible hardware, the accumulation of atoms which came out from the factory. This is fine as far as definition ...


2

Public key cryptography is for when there are several distinct entites, i.e. he who decrypts is not the same person than he who encrypts; similarly, when we want people to be able to verify signatures without granting them the technical power to produce signatures of their own. Public key cryptography is not inherently "more secure" or "less secure" than ...


2

Is it possible to establish a true SFTP connection over the already established and authenticated https link somehow? Yes, if you rewrite the HTTPS implementation in the server and client, and write a custom SFTP client, and solve the problem of sharing a socket across different processes.... Why don't you just use HTTP (over SSL) to upload the file?


2

Disclaimer: I am not a cryptographer. Someone *ahem* Bear *ahem* will probably write a more complete answer. I will like to just point out a few points. But AES had the significant advantage that the standard it was replacing was demonstrably weak against modern computer hardware and in dire need of replacement. Most new protocols or algorithms don't ...


2

As explained in RFC 3920 (section 5), a machine will send the "<starttls>" tag to indicate that it supports SSL/TLS, and then, when the final ">" of a subsequent "<proceed/>" XML element is sent and received, the underlying connection is immediately hijacked to begin a TLS handshake. The handshake consists in TLS messages (which are not XML at ...


2

Technologically, there is no reason that later classes of bluetooth (2.1 and after) shouldn't be able to be used securely. The 2007 E0 vulnerabilities were addressed in alterations made to the bluetooth spec for 2.1 and later and encryption was made a required portion with alterations made to the pairing process. Given a secure pairing (which can be ...


2

You have a few options: First one that comes to mind is creating an SSH tunnel from your Windows Server to your Syslog Server and sending your syslogs to localhost:1514 which would tunnel to logserver:514. This would encrypt your Syslog data in an SSH tunnel. You can do this several ways, like a batch script on startup to invoke PuTTy, like this ...



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