Cryptography is the practice and study of logical means used to achieve information confidentiality, integrity and authenticity. It covers, among other things, encryption (making some data unreadable except for those who know a given secret element, called a key), data hashing (in particular for ...

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Can a botnet be used to effectively break encryption keys?

Can a botnet amass and coordinate enough computing power to break encryption keys that are typically considered to be secure (through brute force)? If this is the case, do we need to make our ...
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1answer
75 views

Calculating the breakability of a given encryption method

I will soon be doing a very important project for school. The main goal of my project is to find a mathematical way to calculate the breakability of a given encryption method of ciphertext. Is there ...
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1answer
175 views

How are SHA1 and MD5 considered to not protect against collisions?

SHA1 and MD5 hash functions are considered to not protect against collisions while SHA2 is. Is it the size of the message digest that makes this or the algorithm itself? If it is based on the message ...
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1answer
118 views

Why do we encrypt ephemeral Public key in Encrypted Key Exchange

Encrypted Key Exchange can resist off-line dictionary attack Protocol : A ---> B : Ep (PK) B ---> A : Ep(Epk(K)) K is Session Key generated by B PK is an ephemeral public key ...
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1answer
2k views

How can you check if a private key and certificate match in OpenSSL with ECDSA?

I know how to do this with RSA keys (see this article: Determine if private key belongs to certificate?) however I do not know how to do this for ECDSA certificate / key pairs. With RSA keys, the ...
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1answer
1k views

AES 128bit decryption using a key longer than 16 bytes

I got a little problem regarding AES decryption. I have to decrypt some text that has been encrypted using 128bit AES / ECB with PHP mcrypt. The thing is, the key that is being used to encrypt/decrypt ...
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1answer
77 views

Does encrypting the message protect it against length extension attacks

Assuming the following HMAC is used : HMACK(M) = Hash(K||M) = H which is "secret-prefix" hashed function. M is the plaintext message , K is the secret key used The ciphertext is generated as follow : ...
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0answers
142 views

Which keys does a bank typically exchange with a card scheme?

I'm trying to understand the different EMV-related keys that are shared between a bank who issues EMV cards and a card scheme, such as Visa or MasterCard. I understand the bank would typically ...
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1answer
595 views

Minimal HTTPS SSL client in C [closed]

I want to implement an HTTPS client using pure C. I have implemented an HTTP client, and it works just fine. My question is: I know the HTTPS protocol does some kind of negotiation to announce what ...
2
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4answers
434 views

How to prove to friend I have solution to puzzle (without revealing it)? [closed]

My friend Paul set me this arithmetic puzzle: To make 21 from the numbers 1, 5, 6, 7. You can use the operations add, subtract, multiply, divide as well as brackets. You must use each number once. ...
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2answers
349 views

Continued Use of Kerberos

I posted this question over on Crypto.SE, but didn't get any takers and thought it might be more suited for this site as it were, so I'm cross posting it here. I was recently looking through the Mac ...
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1answer
67 views

Multi hash security [duplicate]

Is md5(sha1(pass)) more secure than md5(pass)? For example in case of sqli when attacker cant get our hashing schema, brute force or dictionary attack would be much less efficient. Am i right or is it ...
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2answers
148 views

POODLE and REST APIs

Are non-browser applications which do not contain an embedded browser, and merely make REST API calls over HTTPS, vulnerable to POODLE? And if not, is it unnecessary to disable SSL in such ...
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4answers
240 views

How safe is it to use older/unknown Encryption methods for plaintext?

When mailing or chatting with people, it had crossed my mind, what if, for simple communication, someone would use an older encryption method (i.e., ENIGMA), to encrypt their message? Would because ...
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1answer
168 views

Why is not safe to use the same public key in RSA?

In the RSA context, why is not safe to use the same n (public key)for different people?
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2answers
53 views

encryption using two keys

The use case is analogous to accessing a safe box in a bank. There is a per-user key, unique for each user, either generated by the system or hashed from the user's password. And there is a ...
2
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2answers
108 views

Encrypted container on top of a copy-on-write filesystem

The way I understand it, when you write to a copy-on-write filesystem, data never gets overwritten in place, instead new data is written to a new location, and the old data will only be overwritten ...
3
votes
1answer
140 views

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 ...
0
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1answer
172 views

Is (WEP) shared key authentication secure?

I've been reading up on wireless authentication and shared key authentication sounds completely bonkers. I know WEP is very insecure and breaking it with aircrack-ng takes 5-15 minutes but this sounds ...
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0answers
27 views

Infer encoding mechanism from n-grams distance

I have a series of obfuscated strings which across the set of strings have regions of high variance and regions of low variance (implying some encoding mechanism as opposed to an encryption procedure ...
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3answers
2k views

What is the difference between “key length” and “bit strength”?

On occasion, I hear the terms "key length" and "bit strength" used interchangeably. Are these the same things? Or are they different?
4
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2answers
316 views

Using OAuth 2.0 without token storage

I am building a system for a product which requires authentication and authorization. Naturally I have chosen using OAuth 2.0 as it is a commonly used protocol and has proven to be useful. I am ...
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1answer
51 views

Permutation based file secure

I have a thought. 1. Take a file. 2. Read number of bytes. If its less than 2048, padd it till 2048 3. Read each byte. And create a single file which contains the particular byte. Give a random name ...
2
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1answer
268 views

How negative are virtual machines (vms) to /dev/urandom?

I looked at the questions here and here. This then piqued my interest as I've recently been involved with looking into FIPS compliance, and in my vm environment /dev/urandom compliance testing ...
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1answer
78 views

Unlock codes for a mobile app

This is for an Android (via Cordova/Phonegap) game project. My goal is to be able to provide a "promo code" that will allow anyone to unlock the game for free, but I want to limit each code to only ...
1
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1answer
198 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 ...
8
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4answers
805 views

Why the symmetric key is added to the message?

Yesterday in my class we learnt how to send a message from Alice to Bob with the achieved goals of confidentiality, integrity and authenticity. In order to have a better performance we use a hybrid ...
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2answers
810 views

Authentication: Username (email) and password hashed together in one database field

I am currently developping a platform with a PHP framework for our client. The head of the client's IT department wants us to handle authentication with one database field containing ...
4
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2answers
463 views

Encrypt with private and decrypt with public

Above picture is captured from iOS Security overview at page 25. The path encrypt with public and decrypt with private makes sense. But the other path, encrypt with private and decrypt with public ...
2
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2answers
144 views

Difference between Second Pre-image Resistance and Collision Resistance in Cryptographic Hash Functions

I am studying the subject from these notes. However it is not clear what is the difference between "Second Pre-image Resistance" and "Collision Resistance" properties of Cryptographic Hash Functions. ...
29
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2answers
3k views

What actually happens in “low voltage fault attacks”

I understand they are an attack on crypto algorithms as implemented on various processors, but how do they work? The online papers are too complex for me to understand.
6
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1answer
2k views

Two takes on PHP two way encryption - which one is preferable?

I need to encrypt some data and have it decrypted on a later point in time. The data is tied to specific users. I've gathered two possible solutions... 1: The first one is derived from the official ...
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1answer
98 views

Can a known MD5 hash limit the search space for SHA1 collisions?

For a course in game theory, we are dealing with BitTorrent and alternative strategies (roughly alternative clients) we can employ to maximize our download speed. One strategy is to over-report the ...
3
votes
2answers
85 views

Generating encryption key using location data and other hardware data

I'm trying to find information on encryption without key storage, I plan to generate the key using location data, and hardware addresses, so the key is never stored, instead it is generated if the ...
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1answer
2k views

John the Ripper - Calculating brute force time to crack password

I'm using incremental mode (brute force) mode in John the Ripper to crack Linux MD5 passwords. I'm trying to calculate the time it will take to run through all combinations of 12 passwords (with 12 ...
7
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4answers
465 views

Decentralised password recovery

Are there good/established techniques for password/key recovery in situations without a centralised service? (Anything goes, but I'd prefer solutions that distribute the recovery information across ...
2
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1answer
77 views

Figure out if “correct” encryption algorithm was used

Given a database like CryptDB, is it possible to determine whether the data is actually encrypted with the correct (specified) onion? I'll elaborate a bit: CryptDB uses onions (chaining) of ...
0
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1answer
169 views

OpenSSL -nopad with ECB mode

I was just trying to check if OpenSSL does use PCSK5 as documentation states when I got the following problem. I first encrypted a plaintext and encrypted it using DES-ECB. I was expecting to see ...
2
votes
2answers
231 views

NaCL: Encrypt file to multiple recipients

I am trying to understand the Networking And Cryptography Library (NaCL). Consider i have a file that i want to send to multiple recipients. PGP or S/MIME supports multiple recipients by encrypting ...
2
votes
2answers
69 views

Expand key to size of plaintext

I'm taking a cryptology course, and one thing that popped up as an idea was the following: Can't one take a "master" key, and generate a key that is as big as the plaintext, to encrypt the plaintext ...
0
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1answer
290 views

Can anyone with access to root CA private key decrypt HTTPS traffic?

Can anyone with access to root CA private key decrypt HTTPS traffic of sites using certificate signed by that CA ? and if yes do he need to be man-in-the-middle or just monitoring traffic is ...
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2answers
130 views

How is a cypher algorithm verified?

I've always thought about how the symmetric cyphers are verified. Let say I would invent a new cypher. (actually I don't :-)) How should I rationalize its security to the public? As far as I saw ...
3
votes
2answers
205 views

How to store derby database encryption key in HSM?

The Derby Database supports encryption with a key or password. Traditionally this key is stored in the file systems, now I am looking to store and protect this key in the HSM instead, but I couldn't ...
0
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1answer
55 views

Secure shuffles and the rand() function

I'm trying to understand one aspect of a secure shuffle using Fisher-Yates. For reference, here is Fisher-Yates to shuffle an array x of n elements (numbered from 0 to n-1) (from Securing a Shuffle ...
1
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1answer
204 views

Connecting to Oracle Database from VBScript - Hiding Credentials

At work our first level support uses a ticket management system that allows us to add extra functionality via VBScripts that the application invokes. First level support also receives quite a few ...
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2answers
267 views

Why does the finance industry uses 2TDEA instead of 3TDEA?

Why does the finance industry uses 2TDEA instead of 3TDEA; is there any historical reason or technical limitations like the support by HSMs used in the industry? The paper referred to here says ...
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1answer
163 views

Efficacy of self-made ransomware protection

I was recently wondering about how to circumvent malware such as the infamous Cryptolocker a while back and was wondering about the efficacy of having a set of files with known content in a known ...
7
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4answers
1k views

Why secure encrypted data consistency by strong hashing?

Consider the SSH protocol: the SSH packet is like [data, SHA1(data)]. The packet is entirely encrypted by a block cipher. The question is, why do we need a strong hash to protect the packet ...
0
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1answer
105 views

Encrypting the salt with password [duplicate]

Salts are stored in the plain text and readily available with the hashed passwords if the password database is compromised. What if we encrypt the salt using password itself? Doesn't it make offline ...
0
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1answer
164 views

Key Exchange using RSA

I'm trying to do key exchange using the following scheme. Server generates an RSA-2048 key pair and sends the public part to the client Client generates an RSA-592 key pair (I have to use RSA-592 ...