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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1answer
56 views

What does “probability space is over coin flips of algorithm M” mean?

In the book The Algorithmic Foundations of Differential Privacy by Cynthia Dwork, Aaron Roth on page 16 (actually page 20 in the pdf viewer) it says at the very bottom of the page: Definition 2.2 (...
2
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0answers
12 views

hash function notations and existing cryptographic hash algorithms [migrated]

I am implementing Role-based access control by referencing the paper Enforcing Role-Based Access Control for Secure Data Storage in the Cloud. In page 6, they have mentioned to choose hash functions ...
0
votes
2answers
62 views

Which of AES modes are safer and faster for transferring data over the network?

I have using Crypto++ in Qt and use of AES Algorithm for encrypting files. I know about AES modes and their applications. I have use of StreamTransformation method for encrypting files in CBC and EAX ...
2
votes
0answers
24 views

Recommended Crypto Security Setup (Implemented Algorithms)?

Firstly I'm not a crypto expert, however I know how to use algorithms that other people have defined before in practical usages, that is, as long as they live up to their promises. The thing is that ...
2
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1answer
37 views

Android N - Security Crypto Provider is deprecated

As mentioned in "android developer's blog" , http://android-developers.blogspot.in/2016/06/security-crypto-provider-deprecated-in.html , security Crypto provider is deprecated on Android N. And also ...
1
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2answers
49 views

Does a hash of a 32-bit integer make a better hash salt than the integer itself?

I have a scenario where I already have a table of resource passwords stored as unsalted 128-bit hashes. I'm unable to force owners to provide new passwords, so I'm trying to mitigate the situation by ...
7
votes
1answer
38 views

Does the use of a smartphone's Secure Element really offer security benefits to a banking app?

My bank's Android application allows users to perform financial transactions without the use of the physical token generator (which requires an ATM card to be inserted and a valid PIN to be provided) ...
-1
votes
0answers
42 views

Encrypt a file with Block Cipher in CBC mode [closed]

I have using Crypto++ Library for encrypting files, and use of AES Standard and CBC encryption mode. i know comparison between Block Cipher and Stream Ciphers and Operations of each modes, so i want ...
-1
votes
2answers
133 views

How long would it take to generate a file to match a hash? [duplicate]

A individual file only has a single hash of any specific byte length. But an individual hash can represent a large number of different files. Given a 256 byte hash, how long would it take to ...
3
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0answers
50 views

security of libgcrypt when cross-compiling for windows?

Looking at libgcrypt, specifically secmem.c it seems that it does not account for windows-specific memory handling (e.g. VirtualLock) and in fact there is a very troubling comment: #elif defined (...
4
votes
2answers
61 views

Is CHAP authentication still secure?

Assuming the use of the default hashing algorithm MD5, is CHAP authentication still secure? I appreciate that MD5 is considered broken in terms of collision resistance, but I also understand that in ...
0
votes
2answers
36 views

Can an RSA signature be changed given the public key?

If I were to post on a forum (with potentially malicious administrators) my public RSA key and a small string of text that was signed with the corresponding private key, could someone with access to ...
-3
votes
4answers
203 views

Roll your own encryption - with a twist

I am familiar with Schneier's Law: Any person can invent a security system so clever that he or she can't imagine a way of breaking it. I have read the many posts on this exchange littered with ...
0
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0answers
27 views

ISO 9564 Approved Encryption Algorithms for PIN, why symmetric block ciphers?

I am currently researching best practices in designing a potential PIN management solution for a financial services application and began looking into ISO 9564 as a source of requirements. One of the ...
0
votes
2answers
119 views

I want to encrypt certain entries in a database. Is this a good plan?

I'm working on a web app and want to offer the users the option to "encrypt" their account. This wouldn't encrypt everything related to them in the database. Just certain critical fields. I've ...
0
votes
0answers
27 views

How to determine which form of encryption is used? [duplicate]

I have an application which is developed using classis asp. The password is encrypted in the following format - LHFJOJ1234 Can anyone tell me which format is this? I don't have the source code. So ...
39
votes
7answers
5k views

Exploiting MD5 vulnerability in this PHP form?

I've been practicing in security-related topics and I came upon this problem which I don't understand at all. You receive a form with one input named pass, and this is the code you need to bypass: &...
1
vote
2answers
71 views

Detecting a Crypted executable that is supposed to bypass antivirus [closed]

I've seen many Crypters being advertised to bypass antivirus and they work. The malware crypted by the Crypter evades antivirus detection. How would you programtically or using a tool reliably ...
1
vote
1answer
177 views

Partial decryption using untrusted decryption service

While there are ways to encrypt and decrypt information, most of these seem quite computation-heavy. Because of this I am thinking about splitting decryption into two parts - one is computation heavy ...
0
votes
1answer
52 views

How does (Py)NaCl work exactly?

At the moment, I deal with PyNaCl (Docs) and have a question about it: My situation is that I want to create a server that interacts with clients. Both the server and the client will have a long-term ...
0
votes
4answers
199 views

Which layer of OSI model does end-to-end encryption and decryption happen in a network? Why?

I thought it happens at Layer 6, but some resources state that it happens at either Layer 3 or 4.
1
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0answers
19 views

Substitution Table in TKIP

In TKIP Encapsulation, we divided the per packet key mixing process into two phases. In phase 1, we are taking three inputs i.e temporal key (128-bit session key), transmitter MAC address (48 bits) ...
0
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0answers
43 views

Choosing Key and IV in AES-256

I am working on a real-life project for a firm. I have to encrypt data using AES 256 as per specification. I want to know how are the key and IV are really chosen in real world projects. /dev/urandom ...
0
votes
2answers
95 views

C# .Net most secure way to store RSA Key Pair in Windows

At the moment I am looking into the most secure way to store a private RSA key on Windows. Making it as much usable for the end user as possible, while keeping the security to its highest. As this ...
1
vote
1answer
56 views

Securing confidential information between users

I know there are several issues about encryption, but my case is slightly different Users have confidential information stored on their device They have a RSA key pair The information must be ...
-1
votes
1answer
34 views

Question how PPP with CHAP for Cisco works

I'm learning to configure a simple PPP link with CHAP authentication for two Cisco routers. I'm trying to make sense of how router makes sense of the configuration in this example, as the logic of ...
0
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0answers
15 views

What is purpose of fipscheck utility and fipscheck library on Linux?

So I am messing around with dracut and I am trying to get my Linux system in FIPS 140 mode by passing fips=1 to my linux kernel at the boot time from grub. However, I got confused on why dracut ...
0
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0answers
26 views

How crypto module integrity checks mandated by FIPS 140 standard help to make Linux based appliances safer?

After browsing dracut and hmaccalc rpm package source code I found out sha512hmac utility that is used to do do integrity checks for linux kernel (and other binaries) from initramfs boot stage uses ...
0
votes
3answers
236 views

Disadvantages of using same key for encryption and decryption in symmetric cipher? [closed]

In a symmetric cipher, the same key is used for encryption and decryption. What are some disadvantages of using the same key?
3
votes
2answers
96 views

Is it secure to use a part of the key as IV in AES?

I seen a lot of AES implementation samples wide spreaded over the Internet in almost every language I can recognize. There is one difference that I reflect to be repeated between all. Some of them ...
1
vote
1answer
295 views

How to make sure that the public key has not been tampered with during transit?

I understand how public key infrastructure works. There is a private and public key, and someone may use the public key to encrypt data that can only be decrypted with the private key. However ...
1
vote
1answer
27 views

What are common methods to verify symmetric encryption keys?

How can I be certain the same key that was used for encryption? I have an encrypted payload. I use a key and the decryption algorithm to decipher it. I understand data will be returned whether the ...
16
votes
9answers
6k views

Would an encryption scheme that generates an extra key to be securely stored offsite be a safe backdoor?

Let me be clear first and foremost: I do not think installing a backdoor in security algorithms is a good idea. They undermine the trust in the software and in the company that provides the service. ...
0
votes
2answers
78 views

What's the best place to hide long lived encryption keys

I am considering encryption options for a new Sybase project (internal facing only, sitting in our intranet) for a client that has a security policy that requires all sensitive data to use DB ...
0
votes
1answer
83 views

Handling user login using asymmetric cryptography

Is it possible to implement a login protocol with asymmetric cryptography instead of the hashed password method? For example, while creating an account, the client generates a private/public key pair ...
0
votes
1answer
48 views

X509 / SSL certificates in practise

After learning the theory behind cryptography I'm having quite some problems understanding how SSL or X509 certificates works in practise and I simply cannot find useful information in the internet. ...
1
vote
2answers
134 views

How to determine if a key is a weak key

How to do you decide that a particular key is a weak key? In the case of WEP, the weak keys seem to be those whose initialization vectors are in the form of (B + 3,255,x). Does the condition for weak ...
1
vote
1answer
35 views

Possible number of collisions in a hashing function with constant message size

Jumping to conclusions from my question, can we predict possible number of collisions for a given message in a given hashing algorithm. Say I am using SHA-1 which outputs 160 characters string, and ...
-1
votes
1answer
57 views

Shouldn't multiple images always exist even in most powerful hashing algorithm?

I have a confusion in mind that since in hashing we transform a large string into a smaller fixed size string, so its unlikely that any large string has a unique hash. There had to be collisions and ...
180
votes
21answers
23k views

How can I explain to non-techie friends that “cryptography is good”?

After that case in which Brazilian government arrested a Facebook VP due to end-to-end encryption and no server storage of messages on WhatsApp to prove connection with a drug case, it's become pretty ...
1
vote
2answers
103 views

Does unsecure delivery of keys and certs make a VPN useless?

I had to install an OpenVPN service onto a fresh, disconnected computer, but the keys and certs were delivered through an insecure computer with a highly suspect connection. Let's assume that the ...
1
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0answers
45 views

What is the largest cycle of RSA encryption?

Is there a maximum length of a message before it is impractical to use RSA?
4
votes
0answers
98 views

Which block cipher should be used in TLS 1.2 (while keeping 1.3 in mind)?

I have been looking a bit at the various block ciphers for TLS. As everyone should (pipe dream) have migrated to TLS 1.2 by now it should be considered how to prepare for TLS 1.3, when it has been ...
20
votes
2answers
3k views

Why was DES with 112 bit keys (IBM) reduced to 56?

On the French wikipedia page about DES it says that the original DES algorithm from IBM used 112 bit keys. Why did they reduce this to 56 bits? Edit: ok NSA convinced IBM but today it seems like a ...
0
votes
3answers
65 views

How does the meet in the middle attack work on double DES?

I am having trouble understanding the meet in the middle attack and how it works on double DES. I understand that on single DES the key length is 2^56 but why when using double DES is it 2^57? Can ...
23
votes
2answers
2k views

Why haven't (most of) the Zodiac Killer's letters been decrypted? [closed]

The Zodiac Killer (who, in fact, is not Ted Cruz) was a serial killer in the late 60's and early 70's. The twist is, he would frequently taunt the local press with cryptic letters. Four of these ...
3
votes
3answers
139 views

Methods for determining if a file is encypted?

I am working on a anti-ransomware project. It simply monitors the filesystem, and watches for files being created, and deleted. (also monitors for known ransomware file extensions.) Basic Operation: ...
35
votes
8answers
4k views

Find matching phone numbers without actually knowing them

We have a mobile app that, given two users, needs to let them see what common contacts they have based on their phone numbers. How can we do this in a cryptographically secure way and respecting the ...
0
votes
2answers
96 views

How do data breaches of account login information end up in plaintext?

For example, see this story. Am I missing something here? Are the login details actually still encrypted? I don't understand how it is possible for a data breach of what I assume is encrypted ...
0
votes
1answer
55 views

What are the requirements for private keys in Diffie-Hellman key exchange algorithm

Basically question is: If we have pof size 2048 what sizes for private exponents should Alice and Bob choose and why?