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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Is it possible to produce incorrect Metadata?

There is an app on xposed installer called XPrivacy for android that let's you decide what information you want your device to give a specific app and for information you don't want to give it ...
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1answer
266 views

Is there a widely used protocol which builds on AES/GCM, and defines serialization formats of A, IV, C and T together?

note: Title edited to make the answer more useful to a wider audience I'm reading source code for encrypting files with AES GCM and see the following binary output. AdditionalAuthData IV ...
2
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1answer
201 views

Should generating gpg keys ever result in an identical key to an older key?

I recently had a situation where I lost an old private key (write error; realized this too late). In regenerating keys and replacing the public keys on various sites, I noticed that the public keys ...
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2answers
129 views

If P=NP, what is still cryptographically secure? [duplicate]

I know, I know - "If P=NP" is a really large, high-impact assumption. But this is a hypothetical. I mean, clearly RSA (and similar methods of obfuscation) would likely become totally irrelevant - or ...
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1answer
209 views

Avoiding Replay Attacks on Lightweight Channel

I'm in the process of building a network of small devices (ARM microcontrollers with something like nRF24L01 connectivity). The controllers will be receiving commands from a central system over these ...
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3answers
677 views

Storing passwords in reversible form - a genuine use-case

What's wrong with you, you crazy fool, you're not supposed to be able to retrieve a password in plain text! I know. Hear me out. Assume I've got a service that's similar to Mint.com. For those that ...
3
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1answer
392 views

Is my AES/CTR/RIPEMD encryption correctly implemented?

Below is my encryption implementation in PHP. It's based on mcrypt, and uses AES-128 in CTR mode along with a RIPEMD-128 HMAC for integrity checking. For brevity, I've inlined the functions for ...
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3answers
998 views

How does encryption/decryption work when one generate random key?

I am new to this and want to ask a basic question. Suppose I used my password (say "ABC123") to generate a key using the PBKDF2 algorithm (or any such algorithm). For encrypting a file I'll input my ...
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4answers
1k views

Why are there few (none?) easy to use encryption libraries?

If I search stack overflow for how to safely encrypt data, one of the first hits is someone's custom encryption scheme. I've seen several similar questions on this site, and in general they are all ...
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1answer
108 views
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9answers
53k views

Why can we still crack snapchat photos in 12 lines of Ruby?

Just came across this bit of ruby that can be used to decrypt snapchat photos taken out of the cache on a phone, apparently adapted from here. To my surprise, it worked no problem, considering the ...
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1answer
68 views

two encrypting / hashing case, which one is best

Thinking about these below two cases, which one is best and most secure one 1st case //key1 generated from static salt and user password, because in case attacker don't know about source code (bad ...
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3answers
300 views

Can RSA keys be swapped?

On a theoretical level, is there anything inherently different about public vs private keys? During RSA key generation there are two keys generated, key A and key B. Key A is private and Key B is ...
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2answers
161 views

What is truly unbreakable these days? [closed]

Just very curious, count my knowledge in cryptography, algorithms, and security in general as non-existent. Now I am aware that this might be a VERY broad question, but here it goes. What is the most ...
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1answer
116 views

is this code valid for securing passwords? [duplicate]

i was wondering if this is a secure method for a hashing password.if it is not secure please tell me what to do in order to make it secure $pass='test'//the password ...
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1answer
97 views

Theoretical key encryption question

I have a question regarding encryption and message sending. There are 2 hosts, A and B with their own secret key kA and kB (assuming this is not PKI). It is known that when A wants to send a message ...
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3answers
1k views

What is the correct way to make a password salt?

I've made the below function to make a completely random 64 character long hash function password_salt($password){ $salt = hash("sha512", mt_rand(1,100000) . strtotime("now") . $password . ...
135
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8answers
18k views

Why are salted hashes more secure?

I know there are many discussions on salted hashes, and I understand that the purpose is to make it impossible to build a rainbow table of all possible hashes (generally up to 7 characters). My ...
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1answer
168 views

Is it possible to insert data into UUID?

Is it possible to insert arbitrary data into UUID? Let's suppose we have an MD5\SHA hash of something... can we encode that data into a valid UUID?
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1answer
64 views

Frequency Analysis [closed]

I have started looking into Crytography, and the obvious starting point is frequency analysis. As a task for myself I thought it would be good to compile a script which could be used for perform the ...
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1answer
101 views

Root certifcate from an CA company which can be encrpyted by SoftHSM

Does anybody know a CA company which allows me to put the bought CA certficate inside SoftHSM (the same as an HSM but without any hardware, it is pure software)? Is it hard to work with the PKCS11 ...
2
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0answers
38 views

Snapchat clone: How do I secure pre-downloaded notifications so that they cannot be opened outside of the app? [duplicate]

Say I'm making a snapchat clone app for Android and iOS. Let's say that I get a snapchat from Baz. I want to pre-download the audio for this snapchat. However, as the developer, I want to secure this ...
0
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5answers
184 views

Snapchat clone: How do I secure pre-downloaded notifications so that they cannot be opened outside of the app?

Say I'm making a snapchat clone app for Android and iOS. Let's say that I get a snapchat from Baz. I want to pre-download the audio for this snapchat. However, as the developer, I want to secure this ...
0
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1answer
380 views

In regards to GPG4Win, what does “use NAME as default secret key”?

1- what does "use NAME as default secret key" do in Kleopatra tool options? The reason why I ask this, is I have a looooong password for my certificate. And apparently this becomes a hassle when ...
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4answers
4k views

inquiry about SHA1 with RSA for certificate signature

As you all know, plenty of X.509 Certificates use (PKCS#1 SHA1 with RSA encryption) as the Certificate Signature Algorithm for generating the signature of 2048 Bits long. We know that SHA1 hash ...
3
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1answer
76 views

Are there any fast Homomorphic Obfuscuation techniques available?

Assuming that cryptography falls into one of three areas: Awfully weak protocols and algorithms, that are trivial to break with a low amount of effort and resources Cryptographically strong ...
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2answers
229 views

Using 1-day expiration GPG keys only… any disadvantages?

From the thread Does GPG key expiration add to security? , we know that the faster the keys expire, the greater our security. The minimum expiration for a GPG key seems to be 1 day. Thus, isn't it ...
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3answers
283 views

How to hide the sensitive data from the developer of the application and the DBA of the database

I have simple situation, we are in IT center and I need to develop a simple one form 4 fields that contains a salary field, I need the programmer of our IT center could not know the salaries of other ...
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2answers
165 views

Does Known plaintext attacks lead to exposure of the key?

The back-story is long and boring so I will get down to the meat of the argument. I say that if a professional code breaker has a bunch of data, the encoded version of said data and the encoding ...
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4answers
724 views

Secure communication between server and client [duplicate]

I'm writing some security software, and don't want anyone to be able to intercept data as its passed from client->server, and server->client. The best way to do this is over HTTPS via SSL. However, ...
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1answer
94 views

Public Key Cryptography : Key length

While symm. crypt. has around 256 bits of a key, why does public key crypt have a key that is much longer (1000's) ???
11
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2answers
2k views

Describe an example of indistinguishability obfuscation or functional encryption

As described in Perfecting the Art of Sensible Nonsense, a major breakthrough in cryptography research was published in the summer of 2013: Candidate Indistinguishability Obfuscation and Functional ...
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1answer
335 views

Hashing Passphrase in Client-Side JavaScript Rather than Server-Side — Is it Viable?

Yet another salting-and-hashing-for-web-sites question has been left on the doormat of Information Security's StackExchange. The oft-mentioned approach for website password-handling is to use a ...
3
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1answer
48 views

Storing original length of encrypted message

Does storing the actual length of the message in metadata make an encrypted message more vulnerable to attack?
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1answer
385 views

Implementation language for crypto

I'm going to implement a small crypto lib/tool. The "do not implement crypto by yourself" rule does not apply here, since this crypto system is new and not implemented yet. ;) So the first step is the ...
45
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3answers
52k views

Is Telegram secure?

There is a new WhatsApp-killer application called Telegram. They said that it's open source and that it has a more secure encryption. But they store all the messages in their servers and WhatsApp ...
3
votes
4answers
205 views

How do clients enroll using SRP?

From what I understand, one of the benefits or Secure Remote Password (SRP) is that is does not require reliance on certificate authorities. In a scenario where clients need the ability to register as ...
0
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1answer
215 views

RSA vs ECDSA for VANET Security

I am doing a project on Vehicular Ad-Hoc Network Security (VANET). The proposed scheme uses electronic signature as a means to authenticating the nodes. Most of the research papers I read suggested ...
11
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1answer
236 views

Securing a prediction about a future event

I want to make a prediction about a future event, but only reveal that prediction after the event occurs lest knowledge of my prediction affect the outcome. For example, suppose Alice predicts that ...
1
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2answers
426 views

why are the first few characters of a DSA Private Key similar?

I noticed most DSA private keys often start with the same few characters, MIIBvAIBAAKBgQD . For example, generate a private key on Ubuntu, by running: ssh-keygen -t dsa -N '' -f /tmp/id_dsa This ...
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2answers
2k views

Cryptography behind chip based credit cards (smart cards)?

Why are chips safer than magnetic stripes? The answers to the above question explain that the chip based cards can not be cloned as the "secret number" is embedded in the chip and protected by the ...
3
votes
2answers
207 views

Hashes of overlapping data - does it make them easier to crack even when neither is cracked

Say I have strings: stringA, StringB, stringC. And I make two hashes: HashA = sha256(stringA + stringB) HashB = sha256(stringB + stringC) For the sake of the argument I'm suggesting sha256 but ...
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1answer
4k views

How to Encrypt Credit Card number for storing it in sql server database according to PCI DSS Requirement?

According to PCI-DSS 3.4 Requirement: Render PAN unreadable anywhere it is stored by using the below methods: One-way hash Truncation Index tokens and pads Strong cryptography with associated ...
1
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2answers
205 views

Hashed Database: Hash Functions

Let's assume there is a database containing names and each name is hashed and the clear-text is deleted. If an attacker were to steal this database, would he/she be able to get the list of names?
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1answer
171 views

Cryptography - Perfect Secrecy [closed]

Assuming you have a block cipher that (when given a 128­-bit key) yields an instance of a true pseudorandom permutation... how can you use that block cipher within the above constraints to achieve ...
2
votes
1answer
317 views

Requiring 2 keys to access a content

I need to use an external service that can only be accessed by password. I don't like the idea of storing the plaintext password on the server, but AFAIK there's not much I can do. Considering this ...
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votes
1answer
194 views

What is the excellence of RSA vs my algorithm [closed]

I was wondering that what make RSA Asymmetric Cryptography Algorithm special. So I wrote a very simple algorithm that do the same work (Generate Public and Private Key) Now I want to ask you that What ...
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2answers
258 views

Is AES feasible for secure hashing files? [closed]

There was already a similar topic "Why AES is not used for secure hashing, instead of SHA-x?", but it was not about files specifically, and I, personally, am not convinced by the answers in it. "AES ...
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3answers
139 views

How to guarantee privacy on files that I store

I want to create an Android app where users from an office (typical use) can upload scanned documents to the app backend service for later use. e.g. A lawyer want to upload a sentence ...
11
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2answers
507 views

Forward secrecy for kids

In the Scouts, it is popular to use secret codes to write messages (which are simple ciphers). I want to introduce Forward secrecy to the kids so they can use it with these ciphers. So, if the ...