Tagged Questions

The Advanced Encryption Standard (AES) is a symmetric-key encryption standard adopted by the U.S. government. The standard comprises three block ciphers, AES-128, AES-192 and AES-256, adopted from a larger collection originally published as Rijndael.

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Encryption and HMAC with the same password

I need to send authenticated ciphered messages by using a single password. Reusing the same (derived) key for the block cipher and the HMAC is not a good practice, I know. My initial idea is to ...
3
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1answer
65 views

Is it a good idea to do double AES encryption with 2 different keys, when one is held by the user and one stored on the server?

I'm building a web app. The app needs to keep certain data within the database very secure. Please assume for the moment that I don't have a HSM or Key-Management facility and can't afford to ...
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2answers
48 views

Steps for building a good File Encryption on Android

I want to be able to build a good file encryption on android for a cloud app. The files used are mainly pdfs, pngs, docs, audio, video, etc (all sorts of files). Edit: My constrains are that it ...
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2answers
82 views

Should I use HMAC in this situation

I need to store a big message encrypted on a server. What I am about to do is: Encrypt the message with a AES key; (Authentication) Hash the message with SHA512 and encrypt the hash with RSA priv ...
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1answer
67 views

Hardware Implementation of Encryption Algorithm

In the abstract of the AES-GCM RFC, the following passage is prominently included: [AES-GCM] can be efficiently implemented in hardware for speeds of 10 gigabits per second and above... Is the ...
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1answer
87 views

Hardware encrypted external HDDs

I'm planning to buy an external HDD with hardware encryption, namingly the WD My Passport Ultra 2TB. On the WD website the information about the encryption is sadly scarce so I'm asking here. How ...
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3answers
63 views

Can AES encryption prevent modifying bits in a wireless protocol?

I'm building an application with NFC which is a wireless communication protocol. An attacker can modify bits in a wireless communication protocol. I want to prevent this. I know we can't prevent an ...
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0answers
55 views

Is it safe to store the AES passphrase encrypted with the resulting AES key?

I found out that an encryption tool encrypts and stores the passphrase entered by the user and used to generate the AES key in addition of the encrypted payload. Pseudocode: key = md5(passphrase) iv ...
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0answers
57 views

Is it possible to encrypt Word Docs with something other than default?

AES 128-bit advanced encryption is fairly simple to break and was wondering if there was any way to use a more secure one? And if so - any suggestions?
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3answers
94 views

AES Key Management / How To Swap Encryption Key

I'm currently using AES 256 for the encryption of my web application and the security policy context specifies that the encryption key must be replaced once every few months. When that happens what ...
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2answers
119 views

Can we hide a constant hashed key used for AES encryption of a password?

Are there any methods in java to hide a constant hashed key which is embedded in a class? FYI, the key is used to AES encrypt a password used to authenticate a Web Service which would only take a ...
0
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1answer
93 views

How can I safely include the encryption key in the encrypted file?

I am encrypting text files using AES256 (no particular reason, that can easily be changed). Before granting access to a file, I need to verify if a party knows the correct key, but without necessarily ...
2
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1answer
155 views

Python implementation of AES and SHA256/512 that are FIPS-140-2 validated?

For security purposes I need to use AES encryption and SHA256/512 in my Django/Python project. I know there are various libraries out there that provide different encryption methods but I can't seem ...
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1answer
114 views

Is there a benefit to encrypting a file multiple times? [duplicate]

If I had to store a text file with some confidential information on the cloud, would encrypting the file multiple times (say, 3) with different passwords using WinRAR (AES with a 256 bit key) provide ...
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2answers
160 views

Which encryption technique should be used for cloud computing data transfer?

I want to setup my application for cloud computing for Software as a Service. There is going to be a lot of data transfer between my server and client, to and fro. The technique I have envisaged is: ...
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2answers
240 views

Why do the banks all use weaker TLS suites? [closed]

I've been checking out various TLS certificates lately and noticed that most of the banks seem to have the following two issues: 1) They do not offer perfect forward secrecy 2) They are still using ...
3
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3answers
172 views

Is there any security gain / risk by adding additional padding (beyond what is required) when using AES-256 to encrypt very short strings?

I would like to encrypt some authentication tokens using AES 256 (not tied to this algorithm but it seems to be a reasonable choice). These messages are usually very short at 128-256 bits. I'm ...
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0answers
31 views

Possible CPA or CCA attack when using AES-CBC mode under the following situation?

Both client and server know a shared key in advance. Both sides us EVP_BytesToKey() derive a pair of same key and same IV. Then, client and server start transferring data encrypted by AES-CBC mode ...
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1answer
102 views

Are temporary files an issue when opening and editing an encrypted 7z file?

I am new to security and encryption. I want to store important information like passwords and pin codes so I don't forget them. So far I have been using LastPass but I would prefer a solution I ...
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2answers
102 views

How to Conceal/Detect PGP Symmetric Algorithm Used

When Symmetrically encrypting a file, (not signing, not an asymmetric encryption question), is it possible to conceal the encryption algorithm used, or is it already concealed, but just showing on ...
4
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2answers
1k views

Extract AES key by comparing plaintext and encrypted data

Is there a kind of analysis which would enable me to get AES key which was used for encrypting arbitrary data while I have both original and encrypted version of data ? The problem is that the AES ...
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2answers
249 views

Client-server encryption technique explanation (TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 128 bit keys)

I opened a web page using https. When I looked at the page info provided by my browser (Firefox) I saw following: Connection encrypted: High-grade Encryption ...
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0answers
49 views

How does Spideroak manage encryption keys

I'm trying to understand the following from SpiderOak's engineering page (sorry I'm on a mobile phone so have no access to formatting functions like quote blocks): "SpiderOak uses a nested series of ...
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1answer
232 views

Using AES as a Stream Cipher

I need to send a lot of small messages that are usually between 128 bits and 256 bits long, and each message is encrypted with a separate 128 bit AES key. Therefore, to send each message with the key ...
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1answer
79 views

Will obtaining password hash compromise derived encryption key?

I've been looking at how PBKDF is used to generate encryption key for AES. One thing I couldn't get my head around is that how those OS keep the encryption key safe apart from using hardware modules. ...
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1answer
280 views

PHP/Ajax Data transmission security

I'm learning about web security mechanisms. I have developed the following system in PHP and JavaScript: assuming that I have a page named: messages.php which is a real-time chat system. first when ...
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2answers
169 views

Security sanity check

A company whose services I'm trying to integrate uses this protocol: An AES key is embedded in an Android library. To authenticate itself, the library sends a SHA1 hash of the key over plain HTTP. ...
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1answer
54 views

In TLS1.2 AES-GCM mode, what happened when input is not exactly the multiple of its block size?

I know that AES-GCM mode does not need padding, and its output are exactly the length of input data plus the tagging. But I am a little bit lost, as AES itself is block cipher, it could only operate ...
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2answers
122 views

Saving passwords decryptable for later usage

I'm in a situation where I need to calculate a hash of the result of the password in plain text plus some random chars representing a session. The gained hash will be compared to another hash that is ...
2
votes
1answer
122 views

Properties of AES Encryption

First of all, I apologize if these questions can be answered using a web search, but I'm sort of a crypto noob and don't know what to search for. Given N AES encrypted messages (where the message ...
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vote
1answer
157 views

How to decrypt a file when I have its key?

How could I decrypt a file (encrypted with AES-128) using openssl ? I do not remember the passphrase I used to encrypt it, but I saved the key generated and used to encrypt my file. How could I use ...
1
vote
1answer
192 views

256 Bit Key into AES 128 same output as 256 Bit Key into AES 256

I have two different crypto libraries I created, one is in java and uses the standard built-in java crypto libraries. The other uses openssl and has been wrapped in java through the JNI. I'm ...
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0answers
87 views

get encryption key from encrypted and decrypted data

I used encfs to encrypt some important files on my system , But sadly i forget the encryption key , i still have a version of some of the the encrypted files .so my question is : is there there a way ...
5
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3answers
117 views

AES256, repeated IVs and mostly-costant payload: how ok/bad is that?

I recently came across an application that more or less does this: starts from a (supposedly unknown to others) key generates a random IV encrypts some smallish (~ 160 bytes) payload with the key ...
3
votes
1answer
116 views

When to use HMAC alongside AES?

One of my clients wants to provide an URL to each of his customers to register in a system. This URL would contain a query string parameter with some data (e.g. code, email and name) from his clients ...
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1answer
349 views

Cracking Kingston DataTraveler vault privacy - is it possible?

I have Kingston DataTraveler vault privacy USB flash drive (DTVP/2GB). Here is tech specs. Flash drive has a 256-bit AES hardware based encryption. My flash has password protected and I do not know ...
4
votes
1answer
216 views

How are chosen plaintext attacks against ECB implemented in the real world?

Reading up on attacks against AES i have seen countless examples of why ECB is bad, and the logic behind it i can understand, but i can't get my head around how these attacks actually work in the real ...
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1answer
108 views

Do we have to take algorithm substitution attacks seriously?

Bruce Schneier's blog drew my attention to algorithm substitution attacks which may leak symmetric keys through IV or padding or other covert channels, encrypted with escrow keys. The major premise is ...
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1answer
69 views

Gmail Voicemail Encryption

I want to listen to my voicemails in a secure but convenient fashion. I plan do this by having my PBX encrypt the voicemail using openssl aes 256 cbc with salt and a single static password. The ...
4
votes
1answer
287 views

How did SSLv3 get AES?

IANA maintains a registry of TLS cipher suites at TLS Parameters. TLS provides TLS_RSA_WITH_AES_128_CBC_SHA, its value is {0x00, 0x2f}, and its available in TLS 1.0 and above. The AES cipher suites ...
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2answers
437 views

How long would it take to bruteforce an AES-128 protected pdf knowing the key is 20 letter long and that the charset is A-Z,0-9?

The question says everything, knowing that a pdf is protected using standard Adobe password encryption that comes with Acrobat Pro (which as far as i know is AES 128) how much would it take to ...
2
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1answer
128 views

What cryptosystem makes the encrypted text look like random noise?

Suppose one wants to setup a cryptographic protocol in which 2 parties communicate using an encryption scheme that produces encrypted messages indistinguishable from random data (the desired property) ...
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2answers
118 views

Expiring AES Key

Is there any way to make an "expiring" AES key? Here's scenario to give a better picture: Say Bob has some data which he would like to share with Alice. Alice has a public and private key, let's say ...
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3answers
349 views

Java AES encryption output length

I am trying to encrypt few database columns (string values) using Java AES algorithm. This is to protect certain sensitive data. For some users these data should decrypted. In Java AES encryption, if ...
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0answers
44 views

BKSQ block cipher

I'm trying to implement the BKSQ block cipher (similar to AES) but to do so I need the inverse mixcolumns operation, therefor I need to inverse the 2x^2+2x+3 operation. e.g for the AES it is c(x) = ...
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2answers
190 views

Which AES key length to choose for OpenVPN?

I plan on using OpenVPN on client devices which are small embedded machines, so I must balance between speed and security. The OpenVPN documentation says that it is "general wisdom that 1024-bit keys ...
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votes
2answers
252 views

Is AES(Rijndael) faster than Blowfish?

I know theoretical that blowfish is much faster than aes. But I benchmarked several algorithms including aes and blowfish for 1MB, 5MB, 10MB etc. files in java 8 platform and bouncy castle library. In ...
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2answers
115 views

Cryptanalysis of encrypted data at rest

Imagine I have a file encrypted using AES CBC mode with a key and a random IV. The attacker access to the encrypted text and the IV used but not the key. In this scenario there is no vulnerability ...
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2answers
80 views

How can I encrypt compressed data safely?

As mentioned in this particular answer, compressing data before encryption may lead to the CRIME attack, especially if the hacker has collected many similar versions of the transmitted data. Let's ...
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1answer
829 views

Why does openssl enc -aes-256-cbc -a -salt increase the file size?

I'm using openssl enc -aes-256-cbc -a -salt for automated differential backups to Amazon Glacier. But I noticed that using this command increases the file size almost perfectly by 35%. In my ...