Encryption is the process of transforming plaintext using a cipher to make it unreadable to anyone except those possessing the key.

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RSA vs. DSA for SSH authentication keys

When generating SSH authentication keys on a Unix/Linux system with ssh-keygen, you're given the choice of creating a RSA or DSA key pair (using -t type). What is the difference between RSA and DSA ...
250
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13answers
29k views

How is it possible that people observing an HTTPS connection being established wouldn't know how to decrypt it?

I've often heard it said that if you're logging in to a website - a bank, GMail, whatever - via HTTPS, that the information you transmit is safe from snooping by 3rd parties. I've always been a little ...
127
votes
11answers
41k views

Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it?

Why can't a password hash be reverse engineered? I've looked into this ages ago and have read lots on it, but I can't find the explanation of why it can't be done. An example will make it easier to ...
120
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2answers
77k views

What is the difference between https://google.com and https://encrypted.google.com?

Is it there any difference between the encrypted Google search (at https://encrypted.google.com) and the ordinary HTTPS Google search (at https://google.com)? In terms of security what were the ...
94
votes
9answers
57k 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 ...
84
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11answers
20k views

Is there any technical security reason not to buy the cheapest SSL certificate you can find?

While shopping for a basic SSL cert for my blog, I found that many of the more well-known Certificate Authorities have an entry-level certificate (with less stringent validation of the purchaser's ...
72
votes
5answers
9k views

How can my employer be a man-in-the-middle when I connect to Gmail? [duplicate]

I'm trying to understand SSL/TLS. What follows are a description of a scenario and a few assumptions which I hope you can confirm or refute. Question How can my employer be a man-in-the-middle when ...
69
votes
8answers
165k views

How to determine what type of encoding/encryption has been used?

Is there a way to find what type of encryption/encoding is being used? For example, I am testing a web application which stores the password in the database in an encrypted format ...
66
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12answers
22k views

Is Google overreaching by forcing me to use TLS?

Gmail was recently changed to require HTTPS for everyone, whether they want to use it or not. While I realize that HTTPS is more secure, what if one doesn't care about security for certain accounts? ...
66
votes
3answers
71k 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 ...
64
votes
14answers
9k views

Ensure that a file can only be decrypted after a specific date

Are there any cryptographic schemes/protocols that would allow me to encrypt a file, make it publicly available, but ensure that it can only be decrypted after specific date? I assume it would be ...
64
votes
5answers
23k views

Is sending password to user email secure?

How secure is sending passwords through email to a user, since email isn't secured by HTTPS. What is the best way to secure it? Should i use encryption?
62
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7answers
18k views

How hard is it to intercept SMS (two-factor authentication)?

A lot of two-factor authentication mechanisms use SMS to deliver single-use passphrase to the user. So how secure is it? Is it hard to intercept the SMS message containing the passphrase? Do mobile ...
56
votes
4answers
7k views

What kinds of encryption are _not_ breakable via Quantum Computers?

There's the recent article NSA seeks to build quantum computer that could crack most types of encryption. Now I'm not surprised by the NSA trying anything1, but what slightly baffles me is the word ...
53
votes
5answers
14k views

Why should one not use the same asymmetric key for encryption as they do for signing?

In an answer to a question about RSA and PGP, PulpSpy noted this: It is possible to generate an RSA key pair using GPG (for both encryption and signing -- you should not use the same key for ...
52
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6answers
34k views

Can my IT department read my Google Hangouts chats while at work?

Is Google hangouts encrypted? Would my work's IT guys be able see pictures and text I send while on a work computer? Yes I know I shouldn't be sending stuff I don't want them to see while at work, but ...
50
votes
17answers
3k views

Can we still provide confidentiality when cryptography is outlawed?

In certain jurisdictions, use of cryptography by the private sector is limited: e.g. there are reports that in the UAE and other countries not all of the encryption capabilities of the BlackBerry are ...
49
votes
8answers
5k views

Online backup : how could encryption and de-duplication be compatible?

A "soon to enter beta" online backup service, Bitcasa, claims to have both de-duplication (you don't backup something already in the cloud) and client side encryption. ...
47
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5answers
4k views

How does a country block its citizens from accessing a site?

Following Turkey's recent social site blocks, I am wondering how can you efficiently accomplish that as a country. Similar for a big company. Blocking IPs → easy to circumvent, (proxys, tunnels, ...
43
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8answers
8k views

Why can't you work backwards with public key to decrypt a message?

As the title suggests, I am curious to know why you can't work backwards using a message, public key and encrypted message to work out how to decrypt the message! I don't understand how a message can ...
43
votes
9answers
21k views

Are powerline ethernet adapters inherently secure?

I have 2 Zyxel PLA407 powerline adapters. Router is downstairs connected to one adapter, other adapter is upstairs about 30 feet away connected to a desktop. I have a house, not an apartment or ...
42
votes
12answers
6k views

Why should I care if a site uses encryption or not if I'm not exchanging any sensitive data? [duplicate]

Lots of sites these days, that don't deal with sensitive data, enable encryption. I think it's mostly to make (paranoid?) users feel safer. In cases where there is a user's account being logged in, ...
42
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2answers
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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 ...
41
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5answers
82k views

Why most people use 256 bit encryption instead of 128 bit?

Isn't 128 bit security enough for most practical applications?
39
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7answers
8k views

Why isn't open WiFi encrypted?

As far as I understand, WiFi networks that require no password send traffic through the air unencrypted. Those that require a password encrypt each connection uniquely, even if they're all using the ...
38
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5answers
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HTTPS still NSA-safe? [closed]

There are exerpts, that say that using https can be broken by the NSA by now. So is https still a solution for secure web-browsing? source: ...
38
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5answers
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Client-side encryption, but cloud service can still decrypt data in the event of a death? Is this possible?

I've been worried about this password manager, PasswordBox that seems to be gathering quite a bit of steam lately. They seem to have raised VC funding and are offering a free password management and ...
37
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8answers
5k views

How does malicious software encrypt victims' files?

Encrypting a file to me is akin to dealing with a very long string, feeding it into the hashing or encryption function to get another long encrypted string (or a hash in the case of hashing). This ...
37
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9answers
5k views

Is full disk encryption on a server in a secure data center pointless?

I am having a debate with several people regarding how much protection full disk encryption provides. dm-crypt is being used to encrypt data which is required by my company to be encrypted at rest. ...
36
votes
2answers
51k views

How to estimate the time needed to crack RSA encryption?

How to estimate the time needed to crack RSA encryption? I mean the time needed to crack Rsa encryption with key length of 1024, 2048, 3072, 4096, 5120, 6144, 5120, 7168, 8192, 9216, 10240, 11264, ...
36
votes
6answers
4k views

Pattern to allow multiple persons to decrypt a document, without sharing the encryption key?

Current setup We have a service that allows users to upload documents through a website and stores the uploaded documents encrypted on disk. The documents on disk are encrypted with a per-user key, ...
36
votes
3answers
39k views

Is 7-Zip's AES encryption just as secure as TrueCrypt's version?

The main difference being TrueCrypt creates containers and 7-Zip encrypts the file itself, so file sizes can be guessed. Now let's just talk about the strength and breakability of the encryption. ...
36
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5answers
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Advantages and disadvantages of Stream versus Block Ciphers

Encryption algorithms such as Blowfish,AES,RC4,DES and Seal are implemented in one of two categories of ciphers. What are the advantages/disadvantages to the type of ciphers?
35
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3answers
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symmetric encryption session keys in SSL/TLS

This question concerns the session send and receive keys used in SSL/TLS protocol. my understanding is that this key uses symmetric encryption (DES, AES, BlowFish, etc.) I'm wondering, if ...
35
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3answers
2k views

Am I wrong to believe that passwords should never be recoverable (one way hash)?

I recently forgot my password for our cable provider online account, only to discover that they sent it to us via plain text in an email. I quickly sent an email to customer support asking them if ...
34
votes
7answers
4k views

How dangerous might be publishing a public key?

Maybe this question sounds obvious, but I wonder how dangerous might be publishing a public key for an asymmetric encryption system? I know public keys are meant for encrypting messages by anyone ...
34
votes
5answers
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Should RSA public exponent be only in {3, 5, 17, 257 or 65537} due to security considerations?

In my project I'm using the value of public exponent of 4451h. I thought it's safe and ok until I started to use one commercial RSA encryption library. If I use this exponent with this library, it ...
34
votes
3answers
75k views

Understanding 2048 bit SSL and 256 bit encryption

On DigiCert's page, they advertise a 2048 bit SSL with a 256 bit encryption: http://www.digicert.com/256-bit-ssl-certificates.htm What exactly is the difference here and why are two encryption bits ...
33
votes
6answers
34k views

Asymmetric vs Symmetric Encryption

I am currently taking a principles of information security class. While talking about different encryption methods a large number of my classmates seem to believe that Asymmetric Encryption is better ...
33
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3answers
9k views

What is the best home wireless network encryption algorithm to use?

What is the best home wireless network encryption algorithm to use? I realize the best answer will probably change over time, and hopefully people can provide updated answers as new standards come ...
33
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1answer
5k views

Why does AES encryption take more time than decryption?

While I was studying the time consumed by some methods I found that encryption take more time than decryption. Is this right? I am using AES (the same steps will be taken during the enc and dec)
33
votes
5answers
15k views

How do I verify that WhatsApp is using end-to-end encryption?

Slightly old news: Whatsapp Just Switched on End-to-End Encryption for Hundreds of Millions of Users Is there any test that I can perform to verify that WhatsApp is indeed using end-to-end encryption ...
33
votes
2answers
9k views

Web Application encryption key management

In a nutshell, let's consider a web application which stores some information in a database as encrypted data. While I'm purposely trying to keep this some what generic, here are some assumptions: ...
31
votes
5answers
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Why AES is not used for secure hashing, instead of SHA-x?

As far as I understand, AES is believed to be extremely secure. (I have read somewhere that it would certainly not be broken in the next 20 years, but I am still not sure if the author was serious.) ...
31
votes
4answers
23k views

How does PGP differ from S/MIME?

Is S/MIME an abstracted system for general MIME type encryption, whereas PGP is more for email? Why would I want to choose one over the other, or can I use both at the same time?
31
votes
4answers
16k views

Standards for encrypting passwords in configuration files?

My workplace has a standard that plaintext passwords are not allowed in application configuration files. This makes enough sense on its face, in case someone gets access to the config files they ...
31
votes
5answers
2k views

Password Storage - Self Encryption vs Hashing?

Self Encryption: Encrypting a password using the password itself (as a symmetric key). Basically, by doing this, I'll get random data as an output. Now, in order to retrieve the password from this ...
30
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3answers
2k views

Why do WordPress installations retrieve the crypto secrets remotely on installation?

It seems that WordPress retrieves all the crypto constants remotely (via HTTPS): // setup-config.php $secret_keys = wp_remote_get( 'https://api.wordpress.org/secret-key/1.1/salt/' ); Are there ...
29
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3answers
4k views

Is there any advantage to splitting a password?

I've been reading about the LANMAN (LM) hash and I'm curious about a particular part of the algorithm. The LM hash is computed as follows: The user’s ASCII password is converted to uppercase. ...
28
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4answers
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ECDSA vs ECDH vs Ed25519 vs Curve25519

Among the ECC algorithms available in openSSH (ECDH, ECDSA, Ed25519, Curve25519), which offers the best level of security, and (ideally) why?