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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4
votes
1answer
932 views

Whats the best custom compression method to use when I have SSL?

Suppose I have an application which does encryption using SSL and provided you cannot control what cipher suite is being negotiated, and assuming that I have some custom compression over the data ...
8
votes
1answer
712 views

How to get a 'million rounds of PKCS#8 + PBKDF2' with OpenSSL?

I posted this question Is a passphrase-protected SSH private key susceptible to a dictionary attack? a few days back. An excerpt from the final answer: With PKCS#8 + PBKDF2 and one million ...
13
votes
1answer
16k views

Secure Configuration of Ciphers/MACs/Kex available in SSH

Following on the heels of the previously posted question here, Taxonomy of Ciphers/MACs/Kex available in SSH?, I need some help to obtain the following design goals: Disable any 96-bit HMAC ...
5
votes
2answers
949 views

What's the modp length of diffie-hellman-group-exchange-sha256?

OpenSSH 6.2 offers the following key exchange algorithms by default ecdh-sha2-nistp256 ecdh-sha2-nistp384 ecdh-sha2-nistp521 diffie-hellman-group-exchange-sha256 diffie-hellman-group-exchange-sha1 ...
4
votes
2answers
1k views

Rounds of MD5 and SHA512 Hashing Algorithms

What is the exact number of rounds employed by the MD5 and SHA512 hashing algorithms? According to various sources, the SHA512 hashing algorithm employs a total of 80 rounds ...
3
votes
2answers
449 views

Should I customize my Root CA's thumbprint/fingerprint? (SHA1 or MD5)

My goal is to make a certificate's thumbprint "easier" to verify, and not reduce security in doing so. Given that the RSA-based Bitcoin technology has a concept called a "Vanity address" where the ...
3
votes
2answers
836 views

Encrypt web.config file using Data Protection API

I have encrypted part of my web.config file using the Data Protection API. Now, my question is, what does a hacker need in order to decrypt the web.config file? Does he require physical access to ...
37
votes
2answers
17k views

How secure is Ubuntu's default full-disk encryption?

How secure is the encryption offered by ubuntu (using the disk utility)? What algorithm is used underneath it? If someone could at least provide a link to some documentation or article regarding that ...
1
vote
1answer
220 views

NTRU java attack implementation

I'm researching NTRU cryptosystem and started research based on source code from sourceforge and bouncy castle(java language). Currently I'm reseacrhing attacks on NTRU, based on CVP and SVP. But I'd ...
0
votes
1answer
151 views

The basics of cryptanalysis [closed]

There are a lot of books on encryption. Is there a must read intro, something like Smashing the Stack for Fun and for profit, that more or less everyone reads?
3
votes
1answer
572 views

Can you make a digital signature using the receiver's public key?

My question is, can you make a digital signature using the receiver's public key and then have the receiver verify the signature using his private key? I always thought that in order to create a ...
3
votes
1answer
342 views

MD4 or MD5 speed depends on data or just on data size?

Im just wondering ... Lets say, I want to compute an MD5 hash from a given buffer which is an empty (memset(buffer, ' ', sizeof(buffer));) buffer with size of 512. I also want to compute MD5 hash on ...
2
votes
2answers
2k views

Checking if TLS 1.1 and 1.2 implementation in a webserver is upto standards

I am testing a webserver[proprietary] which offers SSL support and they say it supports TLS 1.1 and 1.2 which i have verified by firing requests from IE with only the target protocol enabled . ...
6
votes
3answers
2k views

How exactly is MD5 vulnerable to collission attacks?

I've often read that MD5 (among other hashing algorithms) is vulnerable to collisions attacks. I understand the collision part: there exist two (or more) inputs such that MD5 will generate the same ...
10
votes
4answers
417 views

How can I audit which type of Block Mode encryption is being used when no source code is available?

Given that there are clear advantages to using some block modes of encryption over another, and I would like to ensure that all software used in the enterprise uses a certain "level" of security I'd ...
4
votes
2answers
93 views

Securing an appliance

Scenario: We are in the position to offer a local appliance to run a version of our proprietary software, which is normally provided as SaaS. Question: What steps can be taken to mitigate trivial ...
4
votes
3answers
397 views

Encrypted files storage. How to simplify the password management scheme?

It's probably dublicate but I can't figure out the correct keywords for search. You can help by just telling me those words, I'm rather good with Google :) I want to develop somewhat like file ...
1
vote
1answer
416 views

Using Apple NSKeyedArchiver class without encryption to save score data locally

first of all I'm sorry for my bad English! I have a question about the security of NSKeyedArchiver, a subclass of NSCoder of Apple Foundation.framework ...
1
vote
1answer
288 views

Fragile digital watermarking algorithms suitable for PDF embedding

I have a PDF file that I want to embed an invisible and fragile digital watermark. What are the suitable algorithms available for this task?
-5
votes
2answers
120 views

Protection of online image file (ancient manuscript) [duplicate]

I am going to protect an image file (ancient manuscript) which will be available online for everyone to download. I want to protect the file in these situations: When it's on the server, I need to ...
-4
votes
2answers
151 views

Steganograpjy or Digital Watermarking [closed]

I would like to use the best algorithm to hide 1024-bits inside an image. What is the best option to implement this? Is it by using Steganoraphy (i.e. LSB) or Digital water marking?
-3
votes
1answer
219 views

Development of asymmetric encryption algorithm? [closed]

I am planning to develop (make some minor changes) to asymmetric encryption (i.e. RSA). Any suggestions please?
4
votes
1answer
391 views

Why was ECMVQ dropped from NSA Suite B?

I've found two mentions on Wikipedia that Elliptic Curve Menezes–Qu–Vanstone (ECMVQ) was dropped from NSA's Suite B however they seem to imply different reasons. One mention is preceded by talk of how ...
7
votes
1answer
485 views

HKDF and key stretching

I thought that all key derivation functions would do a key stretching phase, by iterating some kind of process. But I can't see that process in HKDF. HKDF doesn't do key strengthening? If I have a ...
2
votes
1answer
169 views

AES + CBC to encrypt individual local files, fixed IV?

I am using AES and CBC to encrypt a local files separately. I don't plan to transmit them over any network. What are the risks of using a fixed IV for my encrypting application? The only problem I ...
6
votes
2answers
7k views

Decrypt cipher texts encypted with the same one time pad key

I have two pieces of ciphertext encrypted with a stream cipher using the same key. How do I recover the plaintext of both ciphertext messages without knowing the key used?
0
votes
1answer
278 views

What are the performance and security tradeoffs when selecting “ECC” or “Subgroup” in a U-Prove token?

In one of the U-Prove documents, I remember reading something that compared Subgroups versus ECC and it went something like this (paraphrased): Subgroups Requires a bigger key to achieve equivalent ...
2
votes
0answers
59 views

What flexibility does a “Third party gamma” offer to U-Prove deployment?

The U-Prove SDK has the following comment: (link) // 1: CA-RA split (a party trusted by the issuer provides the gamma value) Given that the Gamma value (if provided) overrides the Attributes value, ...
2
votes
0answers
84 views

In U-Prove, what is the purpose of “Pseudonyms”, “Committed”, and “Scope” values and how are they used?

U-Prove allows for anonymous authentication and authorization without the involvement of an IdP. When a client generates a presentation proof 3 values can be optionally included, but I can't find ...
1
vote
1answer
356 views

Advantages of using a Digital Signature Scheme (DSS) with Appendix instead of DSS giving Message Recovery

I've been looking at the EMV draft specification (pdf) for using Eliptic Curve Cryptography in payment cards instead of the currently used RSA. One thing I've noticed is that they've moved from using ...
1
vote
0answers
76 views

Is this any recognizable encoding or cipher? [closed]

I've been watching the Marble Hornets videos on YouTube (basically, an independent film series about a group of kids chased by the "Slender Man"), and in this video I saw something interesting. ...
4
votes
2answers
101 views

How to be sure content was generated on a specific software?

I am developing an open source software. This software generates content that is sent to a server for publishing. Anyone can get this software and generate content. The API for publishing at the ...
8
votes
1answer
453 views

Build a secure channel without SSL/TLS

I'm looking at possible options to build a secure channel between multiple embedded devices with limited cryptography capabilities and an HTTP server (It could be some sort of web service). 1. ...
8
votes
3answers
3k views

When changing a PGP passphrase, does it only affect the private key?

I am beginning to use GPG for email encryption. If I use gpg --edit-key [keyID] to change the passphrase, what files will this affect? Will it only affect my private key, and thus I only need to ...
1
vote
2answers
235 views

Recommended authenticated stream cipher for minimum overhead?

I'm running my TCP/IP protocol secured by encrypting each packet with AES128/CBC, bundling a SHA256 HMAC over that packet. This causes quite a bit of space overhead for small packets, so at first I ...
6
votes
2answers
218 views

Encrypting an empty database field versus leaving it empty

In a system where personal information stored in a database is encrypted, but one of the fields only contains data in a minority of cases, would it make more sense to leave the field empty, rather ...
2
votes
1answer
83 views

Is it safe to derive an IV partially from the secret data if it is hashed before use?

To help ensure uniqueness of IV's used in a CFB AES-256 cipher, software I know of gathers bits from various sources including the plaintext being enciphered, and runs that through an SHA-256 hash. ...
0
votes
1answer
219 views

Should I run my password through Bcrypt before using it for encrypting a file with AES-256? [duplicate]

I need to encrypt a file with a password that can be memorized. So I was thinking about running the password through some rounds of Bcrypt before using it for AES encryption, so every time I want to ...
2
votes
3answers
136 views

User specified iteration count

I'm working on a PHP authentication and registration system following the standard salt+password = 'auth hash' and using the plaintext/unencrypted username as the lookup field on the initial query. ...
13
votes
3answers
1k views

Multi-tenancy, SSL Certificates, and Subject Alternative Name

The X509 specification allows a CA to issue a single certificate for multiple hostnames, by using the "Subject Alternative Name" extension. From the spec: The subject alternative name ...
-2
votes
3answers
166 views

How often is cryptography cracked in a pentest? [closed]

I'm a newcomer to cryptography and was wondering how often systems are attacked by cracking cryptographic systems in the real world. Is it practical to study cryptography as a hacker?
27
votes
2answers
3k views

Criteria for Selecting an HSM

A very sensitive application has to protect several different forms of data, such as passwords, credit cards, and secret documents - and encryption keys, of course. As an alternative to developing a ...
6
votes
2answers
340 views

Do keyfiles actually add any meaningful security in the presence of strong passwords?

In the context of protecting access to local encrypted files or devices against a determined (and competent) adversary, is there any reason to believe that the use of a key file actually presents a ...
2
votes
1answer
377 views

AES in CTR mode with same random IV to create same ciphertext

I am currently working on a little project. I am trying to generate an AES key with that I would like to encrypt a private RSA key. I have to do it this way. However, I do not want to save the AES ...
3
votes
2answers
4k views

Decrypt from cipher text encrypted using RSA

I am sniffing a client side application traffic and I found some encrypted data. I am not able to decrypt it. Information which I have is Public Key: ...
5
votes
1answer
383 views

Known plaintext; What cipher is being used here? [closed]

plaintext: CANDY VERY CRANBERRY ciphertext: TXOtWjYhVk 8&O$4AmSA plaintext: http ciphertext: cZf. plaintext: http ciphertext: r5Hz This is definitely somehow decodable from ...
7
votes
2answers
351 views

Backup schedule for Encryption Keys

How often should encryption keys be backed up? Should this be done on the same schedule as the encrypted content/configuration? That seems excessive, as the keys do not change as often. Perhaps ...
3
votes
2answers
224 views

Does glibc2 version of the crypt function still use DES for alternative hashing methods?

I'm trying to understand how typical Linux distributions generate the password field for entries in /etc/shadow. I can't figure out what encryption algorithm is being used to produce the encrypted ...
24
votes
2answers
1k views

Does versioning an encrypted file make it less secure?

Suppose I use KeePassX as a password manager, and I store the kdb file in Sparkleshare folder as a way for backing up and syncing with multiple devices. The kdb file in itself would be encrypted, but ...
17
votes
2answers
1k views

Homomorphic encryption used for e-voting?

I was reading wikipedia about homomorphic encryptions, and one part got me a bit confused: "The homomorphic property of various cryptosystems can be used to create secure voting systems, ..." ...