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Questions tagged [file-encryption]

The process of encrypting individual files on a storage medium and permitting access to the encrypted data only after proper authentication is provided.

46
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2answers
98k views

What is safer: ZipCrypto or AES-256?

Like in title: which one of these encryption methods (ZipCrypto, AES-256) is more secure and why? I am asking about it because I'd like to know which should be preferred when compressing files with ...
26
votes
3answers
4k views

Information leakage from the ecryptfs filesystem

I'm wondering what information might be leaked from the ecryptfs filesystem. This is what Ubuntu uses if you check the box for "encrypted home directory" when using the desktop installer, so is ...
14
votes
3answers
1k views

Is it safe to use file's hash as IV?

I'm encrypting some files using AES in CBC mode. I'm also using file's digest (SHA-1) to check that data is decrypted correctly (so I need to store it with file). Is it safe to use this digest as ...
14
votes
1answer
11k views

Is CAST5 still a secure algorithm to use?

I just installed GnuPG for Windows. The documentation says the default symmetric cipher is CAST5. In PGP also, default cipher was CAST5. Is CAST5 secure to use? Any known attacks reported on this ...
14
votes
2answers
47k views

Twofish vs. Serpent vs. AES (or a combo)

I've seen some posts and info online, but they are from 2009, 2010, 2011 or 2012, which is 3-6 years ago, which is a very long time. So I'm looking for an up-to-date answer about which of these is the ...
11
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4answers
7k views

Is it possible to get an RSA encryption key by comparing the unencrypted and encrypted file?

Exactly what the title says. If I have a RSA encrypted file, and the exact same file but decrypted, can I tell the key that was used from that information?
11
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2answers
3k views

Which crypto libraries/programs do we have the most confidence in? [closed]

I have recently begun studying crypto. If it's one thing I have learned it's that we should not implement our own crypto. Therefore we should look to using existing software and libraries. When I go ...
9
votes
5answers
5k views

Tamper-proofing log files

Problem Overview I want to securely store log files so the contents are secret, and they can't be modified without detection. The files will be encrypted using authenticated encryption (AES in GCM ...
8
votes
4answers
1k views

Does exposing algorithm, key size and IV weaken the security?

I am using an encryption program to encrypt my documents. Previously I have used PGP and AxCrypt, so I just wanted to see how this new tool encrypts the file. This tool is keeping parameters like ...
8
votes
4answers
2k views

Switching between AES and a highly performant algorithm

I want to de/encrypt several binary files rather frequently on a normally battery-powered device. My goal is to use AES-256 when the device is AC-powered and a highly performant algorithm when it's ...
8
votes
2answers
1k views

Hash decrypts key, key decrypts cipher… why?

I noticed recently that a couple of pieces of encryption software (TrueCrypt being one of them) don't directly use a hash of the password as the key for the block cipher. Instead, they generate a ...
8
votes
1answer
3k views

What is a safe maximum message size limit when encrypting files to disk with AES-GCM before the need to re-generate the key or NONCE

The general limits from the NIST recommendation are as follows: Maximum Encrypted Plaintext Size ≤ 239 - 256 bits; Maximum Processed Additional Authenticated Data ≤ 264 - 1 bits; This stack ...
6
votes
1answer
1k views

Is ChaCha20 alone sufficient for securing data-at-rest?

I wonder if ChaCha20 alone is sufficient for securing files stored on a disk or should Poly1305 should be used along with it? AFAIK, Poly1305 is used to secure the authentication channel, but for ...
6
votes
3answers
2k views

Can elliptic curve (25519) be used to encrypt file?

This is probably a simple question, but I haven't been able to see it stated anywhere. Is it possible to directly encrypt a file (of any length) with some form of EC using the 25519 curve. I know it'...
6
votes
2answers
10k views

Encryption of big files in Java with AES/GCM

I have to encrypt big files. Say their size ranges from 500mb to several of gigabytes. I would like to use AES/GCM/NoPadding as provided by Java 1.8 since that gives me automatic authentication and ...
6
votes
4answers
2k views

Is Porticor's “homomorphic” key encryption something that can really be done or is it just marketing hype?

Porticor has an interesting file encryption offering for encrypting and decrypting files in an MySQL database quickly. They are an Amazon AWS (Amazon Web Service) Partner Network technology partner ...
6
votes
1answer
464 views

Derivation of many (Key, IV) pairs from random 128 nonces and one secret 512 master key

The ext4 encryption system encrypt files with aes-256-xts. Each file uses two unique keys which are derived from a 512 bit master key and a per-file 128 bit nonce randomly generated when the file is ...
6
votes
1answer
997 views

AES file encryption with PBKDF2. Safe parameters?

I'm developing an application that will use public key authentication to contact some webservice. So the user has his keypair on his computer, and I want that file to be encrypted using AES with a key ...
6
votes
1answer
440 views

Single-purpose symmetric encryption scheme for single files

I'm writing a simple password manager program that will encrypt/decrypt a single file (it's size will most likely stay under a few K). This is my initial file format design: ...
5
votes
4answers
1k views

Alternative to NSA encryption algorithm

I am looking for a strong alternative to elliptic curve cryptography. It should be something that could face quantum computing attacks, but nothing created by the NSA. I heard about isogeny key ...
5
votes
2answers
2k views

Would it be better to split a file and then encrypt, or vice versa?

Assuming that you are paranoid before storing your file (distributed across a shared location), which will be the best case scenario: splitting the file first and then encrypting or encrypting first ...
5
votes
3answers
10k views

Best way to generate a IV for AES-CBC when encrypting files?

The situation is that I want to use symmetric encryption to store some info in files. I'm going to use AES-CBC algorithm. The user is going to remember the password (meaning it will not be stored ...
5
votes
2answers
919 views

Reusing AES-CTR Keys and IVs for File Encryption

I’m implementing some file encryption module with random-access capability and AES-CTR seems the right way to go. I understand that reusing Keys and IVs can expose the file to ‘Stream Cipher Attacks’ ...
5
votes
1answer
2k views

File Hash of Encrypted File

Simple question. I have a source file and I have encrypted it with a certain public key. If I take this exact same source file, encrypt it with the exact same key a few hours later would the file hash ...
5
votes
1answer
2k views

Implementing AES encryption for firmware distribution system

I need to implement an AES encryption for firmware distribution system. I have a bootloader that can decrypt various AES variants (ECB,CBC,CTR). When I approached this I found few issues that aren't ...
5
votes
1answer
3k views

Any good file format alternative to PGP for encrypting data at rest?

I'd like to create an encrypted file that: Can be decrypted on a variety of platforms (mainly Windows, OS X, and Linux) with knowledge of the key. Can be decrypted with existing tools (perhaps ...
5
votes
1answer
290 views

When is it safe to not use authenticated encryption?

I have read the post Why should I use Authenticated Encryption instead of just encryption? When is it safe to not use authenticated encryption? I assumed hard drive volume encryption or per file ...
5
votes
1answer
588 views

Is this a good way to encrypt a file?

I need to encrypt a file, distribute it over an insecure channel, and decrypt it later. Using a symmetric-key algorithm. Here's what I intend to do: Get a password P from the user. Generate a 16-byte ...
5
votes
0answers
453 views

File Encryption (EFS method)

I'm implementing (for learning purposes) a file encryptor, which uses the following method (from http://en.wikipedia.org/wiki/Encrypting_File_System). I have 3 kind of keys: RSA public/private, AES ...
4
votes
2answers
3k views

How to encrypt a file for random access

I am a programmer familiar with C/C++ and Python. Lately, we got an assignment from a team asking us to work on one of their projects: we need to make a small program to encrypt a large file using ...
4
votes
3answers
12k views

What algorithm could/should be used to encrypt files for storage on untrusted servers?

I need an encryption algorithm that works fast on large files and doesn't increase the file size. It should use a key to encrypt/decrypt data. The files will be sent using REST and over HTTPS, but a ...
4
votes
3answers
652 views

Ciphers in CBC mode reveal place of change in plaintext

Theoretically, when using a symmetric block cipher in CBC mode, the current block is dependent on the previous block. Suppose one plaintext is encrypted using CBC, and then one bit of it is changed, ...
4
votes
1answer
2k views

Encrypting (CBC) identical files with same key and different iv, is it less secure?

I would like to learn more about cryptography. Let's say you encrypt multiple files with CBC encryption using the same key, but each file has unique (and pseudo random) iv. Does this weakens the ...
4
votes
3answers
520 views

Reusing IV in AES for encrypting file

Everyone says that you shouldn't use the same IV and Key. Is it safe to use the same IV and Key on only one file. EDIT: I will be using CBC or CFB encryption modes so the IV will be updated based on ...
4
votes
3answers
1k views

Encrypting text file line by line with stable encryption

I want to store files in a secure manner (i.e. no one should be able to decrypt the contents of the file without the secret key) but I also want a diff tool to be able to show me which lines changed (...
4
votes
1answer
727 views

How does partial key escrow work?

It is being speculated that one of the ways that NSA leaker Edward Snowden may have created his "insurance policy" – distributing sensitive documents to various individuals with instructions to ...
4
votes
1answer
2k views

Okay to use OpenSSL to encrypt then sign a message?

I am planning on encrypting a message then signing the message so the recipient can authenticate the source. Reading this article has me concerned that I'm doing something wrong. My current plan is ...
4
votes
1answer
223 views

(How) Can we use HOTP for file encryption?

I recently went through the list of available KeePass plug-ins and noticed one that advertises support for HOTP as a means to derive the database key. Now I trust the developer of this plug-in who is ...
3
votes
2answers
1k views

Capacity of Advanced Encryption Standard in terms of File Encryption

what is the capacity of AES in terms of File Encryption? is it really good to encrypt a large files in AES? ex. I am encrypting a 8GB of File... is it still good to used AES? is it still good to used ...
3
votes
2answers
5k views

How to perform file encryption using 128-Bit AES?

I am confused, how can I encrypt a file using 128 Bit Advanced Encryption Standard? Do I need only to encrypt the file name and it's content or is there something that I need to do to encrypt it? Is ...
3
votes
2answers
397 views

How to design a cryptographically secure file hosting service

How would one go about designing something like Google Drive/Dropbox providing the following features: files are encrypted and decrypted on the client files can be synced between devices the service ...
3
votes
3answers
342 views

A specific way for deniable encryption

I read the summary of deniable encryption on wikipedia: https://en.wikipedia.org/wiki/Deniable_encryption Then I read a question, by doom123 on security.SE: https:/...
3
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1answer
1k views

XOR cipher for encrypting compiled C code

I'm exploring ways of encrypting Intel hex files we send to customers for flashing onto an embedded device. The embedded processor itself has a built-in mechanism that prevents anyone from reading the ...
3
votes
1answer
687 views

How does redundancy in a file effects performance and security of encryption?

Does redundancy in a file or data effect performance and security of encryption? (for example for AES, if not for general case) Is it easier to encrypt something that has high redundancy or something ...
3
votes
1answer
3k views

Encrypt a single file, chunk-by-chunk, each chunk using different key (AES)

Encrypt a single file, chunk-by-chunk, each chunk using different key. I am a security newbie (only took 2 security courses before) But currently I am using this encryption method for my Android ...
3
votes
1answer
568 views

File encryption with AES CTR mode

I understand that encrypting files in CTR mode is not perfectly safe, because it potentially leaves the files open for cryptanalysis, if the attacker has access to previous versions of the same files. ...
3
votes
1answer
134 views

Asymmetric Cryptography Confusion - 'Sign' a file to guarantee its source

What I want to do is use asymmetric crypto to guarantee that a file comes from a source. I have software that runs on lots of wireless devices, and each of those has a license file with an encrypted ...
3
votes
4answers
718 views

Non-malleable file encryption using AES XTS 256?

I'm looking to do file encryption of a bunch of individual files, some small, some quite large. The files will be write-once/read-many, so I could use CBC, however, since the read-access needs to ...
3
votes
1answer
93 views

What is the right notion of security to use for file encryption?

It seems that several file encryption systems do NOT use authenticated encryption. (E.g. gpg --symmetric and boxcryptor as far as I can determine). I understand that this is generally considered ...
3
votes
3answers
451 views

Do I need to generate unique IV for CBC encryption of a file if I encrypt multiple blocks of data?

The situation is that I download a mp3 file (song) and I encrypt blocks of data (4096 bites for example). The output of every encryption operation I save it in a new file. When I play the song (...