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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3answers
103 views

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

In a symmetric cipher, the same key is used for encryption and decryption. What are some disadvantages of using the same key?
2
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2answers
79 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
267 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
24 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 ...
-1
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0answers
39 views

What is elliptic curve cryptography and how does it work? [on hold]

What is elliptic curve cryptography and how does it work? Why is is usefull and how does the computer process it?
0
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0answers
66 views

ECDH Man-in-the-middle active attack [migrated]

We have Alice and Bob. The man in the middle can manipulate(remove, add something etc.) A sent from Alice and B sent from Bob, how can he figure out what the common key K(A,B) is, without knowing ...
-6
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0answers
48 views

I have to decode this Base64 value [duplicate]

This is the Base64 value which needs to be decoded and do tell me how to do it because i also want to learn: DJkfVUyiqKVtLzSmMFOupzHtLzIfo25aVUEiVUIm
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
51 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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0answers
125 views

Rank these ciphers in order of difficulty to attack/crack. Explain your reason? [closed]

Caesar Cipher Vigenere Cipher Rail Fence Transposition Columnar Transposition One-Time Pad
0
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1answer
75 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 ...
-3
votes
0answers
46 views

Bluetooth security when non-paired and/or paired [closed]

I was reading about Bluetooth security online and, seeing the lack of papers about it (especially when compared to Wi-Fi security), I was under the impression it was secured. More specifically, my ...
0
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1answer
42 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. ...
-2
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0answers
89 views

How to break a 32 bit block cipher without key? [migrated]

From what I know Skip32 is the only 32 bit block cipher and I heard its not secure. What do I do or which tool do I use to break a 32-bit block cipher? I did search for this but all I find is attacks ...
-3
votes
0answers
62 views

How Cryptographic engine affect in cryptography? [closed]

I find everything on the cryptographic engine, but I did not get a proper Information related to it
-1
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0answers
49 views

Elliptic Curve Diffie-Hellman (ECDH) Key Exchange in Plain English

Can someone please explain to me what Elliptic Curve Diffie-Hellman Key Exchange is in plain English? Similar to the top answer found here: "Diffie-Hellman Key Exchange" in plain English ...
1
vote
2answers
112 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 ...
0
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0answers
48 views

RSA 3072 is 65,536 more difficult to factor than 2048? [migrated]

If RSA 3072 is equal to 128 bit symmetric and 2048 is equal to 112 bit symmetric then 128-112= 16 and 2^16= 65,536. In that case wouldn't this make 3072 more future proof against quantum computers or ...
1
vote
1answer
29 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 ...
174
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
94 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
vote
0answers
41 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
89 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
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0answers
3 views

How can I show RSA OAEP IND-CPA secure [migrated]

How can I show, that RSA with OAEP is IND-CPA secure by using G,H one way function?
1
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0answers
83 views

Why are MACs not included when defining Protocols? [migrated]

I see often in literature related to cryptographic protocols that MACs (Message Authentication Codes) are not included in protocol definitions. For example: A -> S: {TA, B}KAS S -> A: {TS, ...
0
votes
3answers
58 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
132 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
94 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
0answers
20 views

Should RSA primes p and q should differ in length by “a few digits”? [migrated]

When generating RSA keys in the original RSA paper it is stated: "to gain additional protection against sophisticated factoring algorithms, p and q should differ in length by a few digits" Why is ...
0
votes
1answer
41 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?
5
votes
1answer
88 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 ...
1
vote
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 ...
0
votes
1answer
84 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 ...
7
votes
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.
0
votes
2answers
105 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 ...
0
votes
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 ...
0
votes
2answers
166 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 ...
0
votes
1answer
163 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
vote
1answer
94 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 ...
9
votes
2answers
846 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 ...
1
vote
0answers
30 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 ?
1
vote
1answer
66 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
votes
1answer
93 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
votes
2answers
68 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
votes
1answer
70 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 ...
-1
votes
1answer
63 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.