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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Protecting data through an XOR operation with sufficiently long keys

Suppose two parties S and D would like to protect a communication channel. Therefore, S and D exchange two sufficiently long key sequences SB und DB of random bits over a secure channel [e.g not over ...
6
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1answer
2k views

Consequences of tampered /etc/ssh/moduli

What are the consequences if an attacker is able to modify the /etc/ssh/moduli file?
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1answer
225 views

Does DUKPT support offline mode?

I have been working on the payment side with RSA and AES encryption which I got a fairly well technical understanding of encrypting credit card details. Recently, We adopted a new chip and pin device ...
23
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5answers
3k views

Why is Bruce Schneier recommending symmetric crypto over public key crypto

I just read the article written by Bruce Schneier, the crypto guru. In the article, he says : Prefer symmetric cryptography over public-key cryptography. But, he doesn't shed any light as to ...
3
votes
1answer
253 views

Properly implemented strong crypto systems [closed]

I have read this article about the revelation that in 2010 major encryption mechanisms including big four (hotmail, facebook, google, yahoo) and other encryption mechanisms were broken by NSA and ...
67
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3answers
3k views

Did US and UK spy agencies defeat privacy and security on the internet?

This question is meant as a canonical question in regard to the US and UK spy agencies compromising end nodes and encryption between nodes to spy on people they suspect to be terrorists. However, this ...
3
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1answer
766 views

Hashing passwords before inserting into database

For the last 2 weeks I have been reading many blogs about website security and hashing passwords. Many sites have mentioned the pro's and cons about different ways of doing this, which has left me a ...
10
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2answers
405 views

How do new security and cryptography techniques/protocols avoid the chicken-and-egg problem?

. . .better solutions have been proposed and will be worth considering once they have withstood the test of time (i.e. “5 to 10 years in the field, and not broken yet”). -From Thomas Pornin's ...
10
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4answers
738 views

What was SSL 1.0?

What was SSL 1.0? SSL 2.0 and 3.0 are well-known and well-documented. But what did the SSL 1.0 protocol look like? Wikipedia says there was a SSL 1.0 but doesn't say anything about how it worked. ...
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1answer
206 views

Encrypted data transfer with middle node and asymmetric key

I'm looking forward to pass data from a node A to a node B using asymmetric cryptography, but with one (huge) constraint: When A sends data to B, it is possible that B is offline. I would like to be ...
2
votes
2answers
956 views

Please help verify my understanding of Domain Validation (DV) SSL Certificate

This is what I understand so far from reading various knowledgebase and article about DV SSL. Can anyone please help clarify if any of these is wrong? DV SSL (and SSL certificate in general) is only ...
2
votes
2answers
521 views

Are there any dangers in exposing git sha1 commit hashes?

For a non-public repository, are there any potential security concerns in sharing git commit hashes? For example, when I post a git-related stackoverflow question that involves git commits from ...
3
votes
1answer
144 views

How signature validation would be checked on server side?

Sorry, It may be possible that few things are repeated in my question. I have gone through some documentation/discussion signing an API request and twitter signature documentation As per the ...
6
votes
3answers
646 views

How can I prove that I wrote a certain blog post?

I would like to be able to prove that I wrote the article that resides at a given URL on someone else's blog. Is there a way that I can do this with public key cryptography? I know a bit about the ...
5
votes
2answers
651 views

Designing a cryptographic file-sharing protocol

As a learning project, I am trying to implement a secure way to share files with a friend over dropbox. (I am not looking for existing software, I am doing this in order to learn how to do this ...
4
votes
2answers
598 views

NaCl: US Export Regulations

I'm in charge of a product security in our US based startup and I plan to use NaCl for encryption (well, Sodium, actually). I'm trying to navigate the labyrinth of US export regualtions - something I ...
6
votes
2answers
701 views

How is OTR messaging with Socialist Millionaire Protocol (SMP) protected from Man In The Middle?

So imagine the next situation: Alice wants to initiate OTR instant messaging session with Bob but Joe is Man In The Middle. Alice negotiates a shared secret 'X' with Joe (thinking he is Bob) using ...
0
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2answers
452 views

Using a Common Private Key for Digital Signatures

I have a mobile application and a server. The mobile application communicates with the server through a web services framework via SSL. The mobile application allows customers to pay for ...
3
votes
2answers
445 views

Crypto Browser add-on

What are the known limitations with browser addon/extensions that do in browser encryption vs a native implementation in the browser. The addon would expose cryptographic primitives for use in ...
1
vote
1answer
501 views

Is server-side cryptography with user-only access possible for email services?

I came across the Lavabit High Scalability Writeup and got curious. Do you use any particularly cool technologies or algorithms? The way we encrypt messages before storing them is relatively ...
1
vote
1answer
5k views

Create RSA public, private key pair having numbers generated already

I want to know to to generate working RSA key pair, with correct syntax. Let's say i have already generated somehow my numbers for 512bit key, which are: e = 00065537 d = ...
0
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2answers
280 views

An attempt to overcome the key distribution problem inherent in one time pad cryptography

After reading about the 'imminent cryptocalypse' etc, I started thinking about a cryptographic protocol that would not depend on complexity of mathematical operations (e.g. factorisation, discrete ...
1
vote
2answers
466 views

Is it possible to respect a user's privacy while collecting phone MAC addresses?

In London, there are trash bins that track a phone's MAC address and monitor the users movement from one location to another. I want to see if there is any best practice for collecting private ...
7
votes
2answers
395 views

Salt placement prior to one-way hash

In one-way hashing its common to prepend or append the salt to the secret and then hash it: (salt + secret) or (secret + salt). I was thinking of this metaphor as salt falling on a plate of food. It ...
0
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2answers
458 views

Is there a way to configure WPA2-PSK to provide Forward Secrecy?

Is there a way to secure an wireless connection against a decryption attack where the PSK is known (E.G. Airdecap-NG)? Is it possible to configure Forward Secrecy on 802.11 Wireless Connections?
5
votes
1answer
324 views

AV boot disks and Truecrypt encrypted drives

I was wondering if there were any "how-to" guides on what is needed to modify AV boot disks, such as Sophos, kaspersky, AVG etc in order to load the decryption drivers/bootloader for Truecrypt before ...
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1answer
146 views

Posting public key [closed]

Should I put my public key on my website so that people can securely contact me. I have seen personal sites where there public key is at the bottom of the page such as this site by the computer ...
6
votes
1answer
962 views

Is it safe to use rng-tools on a virtual machine?

I am currently working on an app that needs to create GPG key pairs using the gpg tool. Unfortunately, this tool takes a long time to generate a key pair if there is insufficient entropy/randomness ...
1
vote
1answer
138 views

Software library for 1-2 oblivious transfer?

I'm looking for software libraries that support 1-2 oblivious transfer of a single bit between two parties. Googling seems to bring up lecture notes, explanations, and research papers but not ...
4
votes
1answer
897 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
680 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 ...
11
votes
1answer
14k 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
896 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
408 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
779 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 ...
35
votes
2answers
16k 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
214 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
148 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
551 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
316 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
409 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
384 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
368 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
283 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?
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2answers
117 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
147 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?