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40 votes

Where and how to store private keys in web applications for private messaging with web browsers

You may want to consider using the Web Cryptography API for client-side cryptography in the web browser. Then, you can create a keypair using the webcrypto api, and store the CryptoKey object, ...
mti2935's user avatar
  • 949
9 votes

How Secure is gpg Command Using Symmetric AES-256 From Being Cracked

GPG's AES-256 symmetric encryption is believed to be as secure as it is difficult to guess the passphrase or compromise the machine used to perform encryption and decryption. Guessing the passphrase ...
fgrieu's user avatar
  • 142k
8 votes

What do we need white box crypto for?

It could enable a key exchange based off of symmetric primitives alone. For example, suppose I can provide to you a program that will allow you to perform AES-256 encryption of a single plaintext ...
Ella Rose's user avatar
  • 19.6k
8 votes
Accepted

Side-Channel Attacks in the Cloud

The cloud trend brought its problems. In the classical system, your servers were near to you, so the side-channel capability was limited. They were mostly on the smart-card systems where the card ...
kelalaka's user avatar
  • 48.7k
7 votes
Accepted

Is it safe to store both the AES-related data and the PBKDF2-related data (except passwords) in one file?

All the parameters you've mentioned can be public. Furthermore, only the salt, IV and ciphertext cannot simply be guessed. The IV is generally easy to retrieve once the key is known, so the making ...
Maarten Bodewes's user avatar
7 votes
Accepted

Do storage encryption systems care about size of data?

It's common for encryption algorithm specs to specify a hard limit of how much data you should encrypt with the same key. For example, consider the AES-XTS encryption algorithm, which was designed ...
Luis Casillas's user avatar
7 votes
Accepted

Secondary hash function utility, regarding data destruction?

Specifically, why should hash functions not be used for data clearing? I take it you mean that we would overwrite the storage with output produced by feeding its sensitive contents to a hash function....
Luis Casillas's user avatar
6 votes
Accepted

Can big numbers multiplication be a valid form of encryption?

Given a vector $[S_0 S_1 x_1, S_0 S_1 x_2, ...]$, it is quite easy to recover $S_0 S_1$ (by computing the GCD of the various elements). With that information, the attacker can then recover the values ...
poncho's user avatar
  • 148k
6 votes

What is the purpose of implementing cryptographic algorithms in a token?

In practice, “secrets do not leave the token” is not beneficial. Ouch, I think I would rather like to know where my keys are. This is about the same as saying that you don't care if your house keys ...
Maarten Bodewes's user avatar
6 votes
Accepted

XSalsa20Poly1305 for encryption at rest

While you did not mention the source, here one. Actually, XSalsa family is described in Bernstein's paper; 2011, Extending the Salsa20 nonce, D.J.B. Does the "X" in XSalsa20Poly1305 just ...
kelalaka's user avatar
  • 48.7k
5 votes
Accepted

Encrypted firmware

Loading and using encrypted firmware usually requires one of the following conditions to be met: You have a security (co-)processor and the processor is trusted to follow the instructions given by ...
SEJPM's user avatar
  • 46.1k
5 votes

What is the purpose of implementing cryptographic algorithms in a token?

At least one benefit of tokens is that even if the token is temporarily abused because "the UI device is breached", the key itself does not leak. Therefore, in some applications like server ...
fgrieu's user avatar
  • 142k
5 votes
Accepted

Hide the presence of a key in a key-value storage

Suppose you have a set of key-value pairs $(k_1, v_1), (k_2,v_2), \ldots$. You can store the coefficients of a polynomial $P$ that satisfies $P(k_i)=v_i$. The polynomial can be evaluated at any point ...
Mikero's user avatar
  • 13.4k
4 votes
Accepted

Where to store sensitive keys in a device?

With your constraints, there is no way to safely store keys, and this is from a hardware perspective. If they exist in memory, there is pretty much a way to get them out. If you have a way to update ...
b degnan's user avatar
  • 4,830
4 votes

Secondary hash function utility, regarding data destruction?

Specifically, why should hash functions not be used for data clearing? Several reasons, the main being that there is no need to use one. If you were thinking about reading the data from the device in ...
Richie Frame's user avatar
  • 13.1k
4 votes
Accepted

General idea for storing public/private keys?

The requirements for storing public keys and private keys are quite different. Public keys need to be in a trust store in order to be able to trust them. Care should be taken that an attacker cannot ...
Maarten Bodewes's user avatar
4 votes

What do we need white box crypto for?

We can divide the applications into several categories according to the security notions related to white-box cryptography. Unbreakability: means protecting against key extraction in the worst case ...
Junwei WANG's user avatar
4 votes
Accepted

aWallet Password Manager

Elaborate their claims / point me to some source where I can get an overview of the concepts to eradicate my suspicion This answer will focus on this part of the question: elaborating on the listed ...
Ella Rose's user avatar
  • 19.6k
4 votes

Use a hash-function twice

I read that something like this might be insecure as hashes become less secure the more often you hash them again. While this is technically true, you shouldn't worry about it. This paper has precise ...
SEJPM's user avatar
  • 46.1k
4 votes
Accepted

How HSM stores keys securely

The key is stored physically anyway in the hardware, so access is still possible The assumption is that it is practically impossible to read the keys that reside (permanently or temporarily) inside ...
fgrieu's user avatar
  • 142k
4 votes
Accepted

Self-correcting encryption. What are the essential elements?

if there's an inner-layer error correcting code, will it be able to work without an encryption algorithm based on a stream cipher? Depends on how the inner error correcting code works; what you want ...
poncho's user avatar
  • 148k
4 votes

Side-Channel Attacks in the Cloud

Kelalaka gave a great answer detailing many side channel attacks relvant to the cloud. But it is important to note that none of these are relevant if your secret key isn't in the cloud. If you store ...
Meir Maor's user avatar
  • 11.8k
3 votes

Do storage encryption systems care about size of data?

Everything you need to know is actually in the birthday link you provided. Look at the large "Desired probability of random collision" table in the middle of the page. Assume the simplest of disc ...
Paul Uszak's user avatar
  • 15.5k
3 votes

How HSM stores keys securely

but the key is stored physically anyway in the hardware, so access is still possible Yes, in the end the value of the key is required to perform the calculations. And storing digital data still ...
Maarten Bodewes's user avatar
3 votes

What is the purpose of implementing cryptographic algorithms in a token?

In practice, “secrets do not leave the token” is not benefitial. In order to use a secret, a user needs to upload that secret to a program with a user interface (UI). What actually happens is that ...
SAI Peregrinus's user avatar
2 votes
Accepted

About ORAM initalization and running out of space

Are there any scheme to increase ORAM storage with time while maintaining oblivious? I found this paper that addresses the issue of obliviously resizing: Moataz, Tarik, Travis Mayberry, Erik-Oliver ...
Mikero's user avatar
  • 13.4k
2 votes

security of using digital signature as key derivation material

The keychain was moved to the Secure Enclave, the Apple WWDC 2015 Session 766 transcript states: "We also moved the KeyStore component from the kernel into Secure Enclave and it's that component ...
zaph's user avatar
  • 917
2 votes

security of using digital signature as key derivation material

I'm sorry, but chances are this doesn't work. The reason is of course that ECDSA signatures are usually fully randomized, meaning that there's randomness introduced in between the private key and the ...
SEJPM's user avatar
  • 46.1k

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