Linked Questions

15
votes
4answers
2k views

Why should I sign data that's already encrypted? [duplicate]

My question is about the difference between signing and encrypting. Why would you still sign something if you are already going to PKI encrypt it? Doesn't the PKI encryption inherently provide ...
46
votes
5answers
7k views

Why shouldn't we roll our own?

Why shouldn't we create our own security schemes? I see a lot of questions around here about custom crypto and custom security mechanisms, especially around password hashing. With that in mind, I'm ...
35
votes
5answers
5k views

How to Securely Implement a “Remember Me” Feature?

Assuming you already have a website that implements all of the standard login stuff, what is the correct and most secure way to allow users to automatically be logged in for a certain time period ...
17
votes
4answers
5k views

Password resets - what practices should web services follow?

Many of you may have seen How Apple and Amazon Security Flaws Led to My Epic Hacking, where a Wired reporter's Amazon, Apple, Gmail, and Twitter accounts were successfully hacked. The hacker followed ...
11
votes
4answers
5k views

Does symmetric encryption provide data integrity?

Let's say I have one server that encrypts a file with a symmetric key, e.g. AES-CBC, and sends it to clients that decrypt it. Does that provide data integrity when decrypted? Or is it possible for ...
4
votes
8answers
967 views

Is this a good way to store passwords in a Web Application?

I've been tasked with finding a better way to store passwords and came up with this Algorithm. My understanding of Crypto is not strong enough but can someone check this please? Inputs: Username ...
10
votes
4answers
7k views

What's the standard way to encrypt a file with a public key in Java?

I'm writing a client app in Java that sends encrypted data back to the server. All clients have my RSA public key. Is there a standard way to encrypt a given file with it to send it back to the ...
11
votes
2answers
956 views

Is there any advantage of bcrypt over multiple iterations of SHA-x/MD5?

I know that a good password hashing algorithm should be slow. MD5, SHA256, etc. are fast. So I've been adding multiple iterations of SHA-256 hashing to my web apps (around 50000). Getting the hash of ...
9
votes
3answers
2k views

How can I encrypt a file with .NET and have the same file size of the original file?

I'm using .NET and I've written an awesome routine (xD) that encrypts and decrypts a file using AES256 CBC. It works perfectly, but now they told me that the encrypted file must be of the same size of ...
5
votes
2answers
741 views

Designing a cryptographic file-sharing protocol

As a learning project, I am trying to implement a secure way to share files with a friend over dropbox. (I am not looking for existing software, I am doing this in order to learn how to do this ...
9
votes
1answer
11k views

How to implement an API-Key-Mechanism

first of all: I am quite unsure about the questions title, so if you have a better idea, please feel free to tell (: I would like to know about best-practise examples where services (like Twitter or ...
5
votes
3answers
1k views

Is it safe to use different derived keys but from the same passphrase for AES CBC encryption followed by HMAC SHA256 hashing?

I am working on a cross platform (JS/iOS/Android) list manager application that persists data through a REST API and I want to ensure that any textual data is properly encrypted on the client side so ...
6
votes
4answers
3k 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 ...
9
votes
2answers
1k views

How does the padding scheme impact the security of encryption

After digging a little deeper into cryptography I am wondering what impact the different padding schemes do have an the security of an encryption algorithm. Lets take AES-128 in CBC mode as an ...

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