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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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 ...
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3answers
267 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?
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2answers
101 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 ...
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1answer
304 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 ...
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1answer
33 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 ...
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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. ...
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2answers
97 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 ...
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1answer
86 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 ...
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1answer
58 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. ...
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2answers
148 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 ...
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1answer
37 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 ...
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1answer
58 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 ...
181
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21answers
24k 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 ...
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2answers
109 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 ...
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0answers
46 views

What is the largest cycle of RSA encryption?

Is there a maximum length of a message before it is impractical to use RSA?
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0answers
103 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 ...
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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 ...
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3answers
70 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 ...
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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 ...
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3answers
146 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: ...
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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 ...
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2answers
97 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 ...
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1answer
60 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?
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1answer
124 views

How bad it is to feed /dev/random with /dev/urandom?

I have seen many blog posts, or blog comments which recommends to feed /dev/random entropy using output from /dev/urandom. I'm not a crypto expert, but it looks like a good way to replace hard-to-...
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0answers
52 views

Which is the correct algorithm while checksumming a portion of code?

As part of my research, I came across a technique in a paper which applies checksumming on a portion of code. I want to implement it. Here is the research paper which talks about the checksumming ...
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1answer
115 views

How to verify the signature value in a SSL certificate?

According to RFC 3280 a certificate's basic syntax is Sequence := { tbsCertificate signatureAlgorithm signatureValue } In tbsCertificate, SubjectPublicKey is the public key of the ...
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3answers
1k views

What are the disadvantages of using public key cryptography when encrypting files? [duplicate]

I am wanting to encrypt a file with my public key, my friend told me that this is not a good idea but did not explain why. Can someone explain please.
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2answers
107 views

Is open source a good option for cryptography libraries? [closed]

I am trying to find good cryptography library to use with my project. I found open source options like openSSL and many more and also proprietory options like Intel Integrated Performance Primitives ...
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0answers
29 views

security authentication protocol [duplicate]

I'm "creating" a secure authentication protocol for my system and it is this: C-> S C S-> C N(once) C-> S Kc,aut[N] S-> AUT Ks,aut[C,Kc,aut[N]] AUT-> S Ks,aut[N] the line : X ...
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3answers
258 views

Why don't the majority of today's malware use strong cryptography?

While reading another story of botnet takedown, my wondering has reached its apogee: Why don't malware authors use cryptography (encryption + signing) provided by good libraries when their creations ...
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1answer
327 views

How does the Signal Protocol, used by WhatAapp, work?

I want to understand the process of the Signal Protocol. I have google it, but I am unable to find any good article or tutorial. I want to understand the basic definition and functionality of the ...
1
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1answer
115 views

AES step by step

I can't seem to find an AES tutorial that starts from Unicode to Cipher text. All of the tutorials I found starts with 128 bit block already. Also, where do I start or what topics do I have to start ...
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2answers
880 views

techniques to detect & mitigate Crypto-ransomware?

Crypto ransomware attacks are the latest concerns for our organization, we need to verify if we are adequately protected from them & if affected, what are the generic mitigation measure? How do ...
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0answers
52 views

Create a signed file from the detached signature and the clear text file content

Assuming I have the following: data.txt data.ps7 (the detached signature) Can I generate the bundled signed file ? Any example would be great, using C#, Java or openssl or any other tool ?
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1answer
70 views

Cryptography behind RedHat subscription system (DRM)?

I have to do a project like a subscription manager. Ideally this should work like RedHat subscriptions. I'm having a hard time figuring out how it was implemented. How do they manage to avoid a ...
3
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1answer
100 views

What would be the repercussions in Information security, if someone found a way to factor large numbers quickly?

I am curious as to how exactly cyber-security would be affected if someone found a way to factor a large number quickly into its multiples. Let's assume that the time required for factorization is ...
4
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2answers
71 views

Signature that can only be verified by author and recipient - without pre-shared key

Desiderata: Alice wants to send a message to Bob for him to keep and to be able to refer to, such that Bob can be certain that the message came from Alice and was not tampered with. Alice also ...
3
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1answer
80 views

Is having a unique key to encrypt data not sufficient

Is it necessary to use a unique Initialization Vector (IV) with various cipher modes of operation (e.g. CBC) even though I use a unique key to encrypt plain text every time? It is said that an IV ...
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1answer
67 views

What defines a “good” cryptographic algorithm? [closed]

The title pretty much says it all. I am looking for a formal definition of what a good crypto algorithm is. I cannot find anything online.
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1answer
68 views

how is public key being exchanged in asymmetric cryptography?

I understand that exchanging public key between parties is challenging task in asymmetric cryptography.Can someone help me understand how it is achieved?
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1answer
70 views

Hide data from user, but process it in application

Is there a way to hide the data that's received somehow from the user? In particular, I have some data that gets send from a webserver to an application. I want the application to process the data, ...
2
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1answer
89 views

Question on MAC(Message Authentication code)?

I am new to Cryptography and unable to understand clearly about MAC concept. As per MAC concept, Sender 'A' will encrypt the original message with symmetric key to create MAC1 value and then will send ...
3
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1answer
75 views

Is this good/secure method for client-server communication encryption?

Something came to my mind, and I wonder if this is proper method for client-server communication, and if this method is wide-used. On connection, client generates seed, encrypts it using asymmetric ...
2
votes
1answer
123 views

Can an attacker make in-app-purchases of my products in their app?

My iOS app needs to store a pre-shared secret. It cannot embedded within the App Bundle itself because it could be extracted by statically analysing the bundle. Apple's In-App-Purchase system allows ...
9
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1answer
199 views

How do EMV contactless cards protect against replay attacks?

I understand that standard RFID cards are vulnerable to replay attacks however, how do smart cards which are also contactless protect against replay attacks? Is this decided by the chip or by the ...
4
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2answers
135 views

Does EMV protect against sniffing PAN data from untrusted network?

I have received conflicting information in regards to the security of PAN data on the wire. Can this be sniffed with properly configured EMV at an atm? To quote from the link below: http://www....
2
votes
2answers
118 views

Are there any security advantages to the “TrueCrypt-Paradigm”?

TrueCrypt and its successors use a file format that has the special property, that it looks completely random, there's only a salt (which is random) and the cipher text (which looks random). I like to ...
3
votes
5answers
639 views

Why can passwords be used to encrypt data, but are less strong for authentication?

Encryption software is often password based. Even if the adversary gets your computer they can't get the data without knowing the password, and bruteforcing is infeasible. Websites use passwords to ...
4
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1answer
166 views

What are active research topics in SSL/TLS?

I don't know whether it is right to ask a question here for my MTech dissertation. I thought there is no good place in the world where I can find security experts like here. I am interested in doing ...
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4answers
205 views

How could online encryption ever work? [duplicate]

I have recently read about the german enigma machine in WW2, It worked in a way that every day the machine configuration was sent per mail to the different operators. (I couldn't find official sources ...