Tagged Questions
9
votes
3answers
171 views
Multi-tenancy, SSL Certificates, and Subject Alternative Name
The X509 specification allows a CA to issue a single certificate for multiple hostnames, by using the "Subject Alternative Name" extension.
From the spec:
The subject alternative name ...
5
votes
2answers
76 views
Do keyfiles actually add any meaningful security in the presence of strong passwords?
In the context of protecting access to local encrypted files or devices against a determined (and competent) adversary, is there any reason to believe that the use of a key file actually presents a ...
3
votes
3answers
215 views
Is it okay to sign a PGP key without an IRL meeting?
[PGP] can get paralyzed by excessive analness.
— Phil Zimmermann
Preamble
I am in the process of building my own web of trust. That is, I want people (PGP users…) to be—fairly—sure that, by ...
5
votes
1answer
97 views
Security and authentication problem
We have a sample scenario and we would like to receive some feedback and some solutions regarding possible security schemes.
First of all, lets imagine a real world scenario:
Imagine that a user ...
1
vote
2answers
129 views
How high is the entropy of this salt-generating code? (No code-reading actually necessary)
What is the best method?
Assumption: I have a function that generates a number of medium-high entropy bytes
Step1:
I generate 3 of these medium-high entropy bytes.
Step2:
I hash these bytes using a ...
2
votes
2answers
115 views
Easy protocol for email authentication
I'm cooking up a very simple system to send commands to a remote server via email. Everytime an email is sent to do_something@mydomain.net, the server runs a python script that does something ...
1
vote
4answers
334 views
SSH: reusing public keys and known-man-in-the-middle
Usually, people recommend to use a single private-public key pair everywhere (if we're not talking about a possibility of compromising the private key):
Best Practice: “One per-user ssh key” or ...
1
vote
2answers
210 views
Can I use hardware token OTP to stop piracy?
Our firm sells an offline desktop (.exe) software, we are thinking of using OTP (from hardware token like in internet banking) to stop people from copying the software without permission. Basically, ...
0
votes
1answer
149 views
Storing Private Keys Generated on Server with specific User's Password Securely
I am currently building a system (PHP Web Application Framework) that creates an RSA Key Pair for a user to allow other users to send secure information from one to another. The public key is ...
3
votes
1answer
183 views
Can I re-use another vendor's dual factor token in my own system? (Avoid physical token bloat)
I read the open source multifactor authentication techniques called HOTP RFC 4226 and TOTP RFC 6238 and realized that a single random number is the basis for the token's cryptography... and that this ...
0
votes
1answer
170 views
How does the YubiKey Validation Server work from an encryption perspective?
Many YubiKey servers rely on the free cloud hosted authentication that comes with the product, but I'm interested in keeping all cryptographic material in my control. For that reason I am looking at ...
1
vote
1answer
93 views
Reasonable computationally lightweight security?
I've read a bunch about how one should use bcrypt or PBKDF2 as a good middle ground between tunable workload and acceptable time to make brute force and collision attacks unfeasible.
What if the ...
4
votes
2answers
800 views
When using symmetric key encryption, do we need to sign?
Say we're using a shared key between two parties, that has been distributed using public key encryption, is it still necessary to sign any data that's encrypted using the shared key? Or is it enough ...
1
vote
0answers
132 views
Verifying Authenticode signed executables and DLLs using OpenSSL API [closed]
I have installed openssl and now the rsa_test.c is running fine. What I want to do is:
Open any exe or dll digital certificate. Extract the Thumbprint and PublicKey.
The public key contains the ...
8
votes
5answers
231 views
How do RSA fingerprints protect from MITM attacks?
I understand that RSA fingerprints are used to verify that you are really connecting directly to who you want to connect to, and not someone else posing as that site.
Like when you do a git push, it ...
-1
votes
2answers
109 views
Should I use salt to authenticate data?
I have a client and a server. The client makes a request containing userId, cardId, position (on the card)
A hacker could just do the same http request with the next position. So I think about ...
5
votes
3answers
1k views
HTTP Basic auth password storage more secure than Digest auth
If you are using SSL already, it appears Basic auth is the way to go since you can perform bcrypt with the password when you store it in the database, where as Digest auth only allows md5. As we know, ...
12
votes
4answers
284 views
Why aren't digital signatures the standard way to authenticate web clients?
The web is a mess of incompatible cookie schemes, asinine requirements ("your password must contain letters, numbers, and at least one symbol from !()-_., and must begin with a letter, and once you ...
2
votes
3answers
209 views
Establish a secure channel with mutual authentication given pre-shared public keys
Suppose I have a system whereby parties are identified by their public key (with some pre-selected asymmetric key algorithm). Suppose I have a party PUB1 which wants to establish a secure channel with ...
1
vote
2answers
92 views
How do i use a guessable ID for authentication
This question doesn't fit well in many categories but hopefully someone's run into it before.
I'm developing a web api that will interact with a physical device. Each new physical device has it's ...
-1
votes
1answer
161 views
About important hacks in history [closed]
I would like to know how important hacks happened, because I can figure out how they hacked a website but I can't figure out how did they hacked into NASA International Space Station source code. Or ...
7
votes
2answers
415 views
HMAC Based Request Signing - Storing the Salt
I'm working on a (non high security) project that currently isn't live but might go live at some point.
We have a REST API (implemented using Restlet and Neo4j) running on a server and an Android ...
4
votes
2answers
612 views
MAC vs Encryption
I understand the difference between MAC (eg. hmac_sha256, etc.) and Symmetrical Encryption (eg. rc4, etc.), but my question is what advantage does MAC solve that using encryption doesn't?
I know that ...
3
votes
2answers
426 views
Can we prevent a man-in-the-middle attack with symmetric-key cryptography?
Suppose that Alice signs the message M = "I love security" and then encrypts it with
Bob's public key before sending it to Bob. As well known, Bob can decrypt this to
obtain the signed message and ...
5
votes
4answers
2k views
HMAC/PBKDF2 vs Simple hashing algorithm for web service authentication?
We are in the process of creating a web service and have been investigating ways of securing it. In reality, the service is likely to get very little traffic and the data is likely to be of little use ...
4
votes
1answer
464 views
How secure is TOTP key on phones?
Our company is considering several options in moving to MFA with software OATH TOTP or yubikey OATH OTP. In regards to where the secret is stored, I'm aware that a yubikey or similar hardware device ...
6
votes
1answer
697 views
How will security need to be changed if P=NP?
If we suppose that it is found that P=NP, how will security measures need to be changed?
I'd like to know the major security measures that are affected, and how they would need to be changed. We can ...
5
votes
6answers
839 views
Prevent denial of service attacks against slow hashing functions?
I've been thinking about bcrypt recently, and what I wonder is if there's a way to deal with the inherent (D)DoS problems with slow hashing functions. Namely, if I set up bcrypt so my machine takes ...
1
vote
2answers
198 views
Does secure remote password verifier transmission need to happen out of band?
With relation to the necessity of a verifier being transmitted from the client to the server prior to any handshake steps, I was wondering how this is supposed to happen securely? To me this seems ...
5
votes
2answers
529 views
ssh public/private key pair
I am having problems understanding how ssh really works. I know it uses a public key cryptography to encrypt messages. However, I can ssh to a server without first generating a public/private key pair ...
1
vote
3answers
298 views
Three Message Authentication Protocol
I have a protocol where "A" initiates communication with "B". "B" then sends a challenge to check if "A" is really "A". "B" does not remember sending the challenge so "A" has to respond by sending the ...
5
votes
2answers
212 views
System for Mutual authenticaion and confidentiality
I am looking for a protocol where there needs to be mutual authentication between client and server. For example server should connect to a particular client only. That is client should authenticate ...
10
votes
3answers
423 views
Multiple CAs signing a single Cert/CSR?
Just saw this suggested on Slashdot
So I've seen quite a few people wanting a switch to self-signed certs (who IMO mostly don't understand what making that secure actually involves), and an idea ...
7
votes
8answers
580 views
Is the following authentication scheme secure?
I was trying to design an authentication system that would make it much harder to guess a password via brute force, and reduce the risk to a user if the hashed password was stolen through a snooping ...
5
votes
3answers
250 views
DHE exchange and client authentication
If a server has a known public key and a Diffie-Helman exchange is performed and signed by that key, is there any benefit to authenticating the client before establishing a secure channel instead of ...
6
votes
3answers
605 views
chosen plaintext attacks against MD5 and SHA1
According to http://tools.ietf.org/html/rfc2617#section-4.9, having the server chose a nonce but not having the client chose a nonce opens up Digest Access authentication to chosen plaintext attacks. ...
79
votes
3answers
48k views
RSA vs. DSA for SSH authentication keys
When generating SSH authentication keys on a Unix/Linux system with ssh-keygen, you're given the choice of creating a RSA or DSA key pair (using -t type).
What is the difference between RSA and DSA ...
1
vote
2answers
172 views
TCrypto - Comments about design decisions I made?
I have pushed some code to GitHub to demonstrate the usage of symmetric key encryption in PHP. It is a small key-value storage library and it (optionally) offers ability to encrypt the stored ...
7
votes
3answers
286 views
zero knowledge proof and its protocol
In Zero-Knowledge Proof where we take the analogy of Peggy (Prover) and Victor (Verifier):
In this story, Peggy has uncovered the secret word used to open a magic door in a cave. The cave is ...
25
votes
5answers
3k views
How do some sites (e.g. online banks) only ask for specific characters from a password without storing it as plaintext?
I thought How can a system enforce a minimum number of changed characters... would answer my question, but it seems this is a different case.
When I sign on to my online banking account, I'm prompted ...
6
votes
1answer
196 views
Collision attacks on OCB?
I've been looking into the OCB cipher mode and everything I hear sounds good. I was planning on implementing it.
Everything except for this lone voice, that is: Collision attacks on OCB:
We ...
4
votes
3answers
187 views
Choosing an authenticated encryption cipher mode without associated data
In the application I'm writing there is need for a huge amount of private data transfer on the order of eighty gigabytes, but there is no public data. I'm looking especially to gain ...
4
votes
1answer
215 views
What is the purpose of AEAD?
I think I need to correct some misunderstandings I have about AEAD. What is associated data used for in authenticated encryption?
7
votes
2answers
462 views
Any advantage to securing WiFi with a PSK, other than to keep out unauthorized
As I understand WiFi with a PSK, such as WPA(2)-PSK or WEP, anyone on the same network can decrypt anyone elses packets because everybody has the same key.
In which case, if you are not going to ...
6
votes
3answers
674 views
Is the OpenPGP private key inherently password-protected?
I know I am required to enter a password every time I use my OpenPGP key. Is this done via software implementation or is it a property inherent to the protocol, and therefore the key?
Essentially, ...
3
votes
0answers
204 views
Theory behind RSA SecureID/Lockheed attack
Unless I missed something I don't think RSA/EMC came out and said publicly what was stolen earlier this year when they were compromised. So I know the answers to this question will be conjecture. That ...
32
votes
2answers
4k views
Is a rand from /dev/urandom secure for a login key?
Lets say I want to cookie for a user, would simply going to /dev/urandom, generating a 1024 bit string, checking if it already exists (and looping till I get a unique one) suffice? Or should I be ...
24
votes
6answers
1k views
Is using a public-key for logging in to SSH any better than saving a password?
Using a public/private key pair is fairly convenient for logging in to frequented hosts, but if I'm using a key pair with no password, is that any safer (or less safe) than a password? The security ...
41
votes
5answers
11k views
Certificate based authentication vs Username and Password authentication
What are the advantages and drawbacks of the certificate based authentication over username and password authentication?
I know some, but I would appreciate a structured and detailed answer.
UPDATE
...
5
votes
1answer
606 views
TLS at layer 4 BUT 802.1X EAP-TLS at layer 2?
In the CISSP books, SSL/TLS has been through the arguments and fell rest onto the transport layer 2 instead of the session. OK - Fine.
Port security 802.1X and EAP is a data link layer 2 ...
