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 ...
286
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13answers
36k 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 ...
166
votes
8answers
26k views

Why can't the FBI read the key embedded in the iPhone's secure chip/ROM directly from hardware (silicon)?

As far as I understand, the 4 digit passcode is combined (in some fashion) with a key stored in secure read only memory (e.g. secure enclave chip or similar), where it is directly embedded into ...
157
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6answers
18k views

Apple's open letter - they can't or won't backdoor iOS?

Apple released an open letter to the public outlining their reasons for not complying with the FBI's demands to modify the iPhone's security mechanism. Here's a summary: The FBI has an iPhone in ...
150
votes
11answers
55k 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 ...
147
votes
2answers
91k 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 ...
125
votes
5answers
120k 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 ...
104
votes
13answers
27k 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 ...
96
votes
9answers
63k 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
votes
8answers
16k views

If a provider sees the last 4 characters of my password, can they see it in full?

I have some domains/websites as well as emails with Bluehost. Every time I need support, they need the last 4 characters of my main password for the account. They cannot tell me how they store the ...
82
votes
15answers
17k views

Why would someone “double encrypt”?

If I have a website or mobile app, that speaks to the server through a secured SSL/TLS connection (i.e. HTTPS), and also encrypt the messages sent and received in-between user and server on top of the ...
79
votes
8answers
212k 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 ...
78
votes
5answers
12k 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 ...
74
votes
5answers
11k 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 ...
71
votes
5answers
31k 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?
69
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7answers
24k 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 ...
68
votes
12answers
23k 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? ...
67
votes
16answers
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
116k views

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

Isn't 128 bit security enough for most practical applications?
61
votes
5answers
18k 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 ...
60
votes
2answers
7k views

Why has the NSA had a hand in deciding on encryption standards?

The NSA has had a large hand in the design of at least two significant encryption standards: the Digital Encryption Standard, and its successor, the Advanced Encryption Standard. Because of their ...
55
votes
6answers
49k 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 ...
53
votes
2answers
37k views

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 ...
52
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8answers
6k 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. ...
51
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
2answers
6k views

How is WhatsApp sending end-to-end encrypted messages in push notifications?

WhatsApp implemented end-to-end encryption (whitepaper) in their latest update. How is it possible for WhatsApp to send push notifications with message contents to the Apple Push Notification ...
48
votes
9answers
12k views

Writing my own encryption algorithm [closed]

I am currently studying IT at college (UK college aka not University) and the coursework is boring me to death. I have been coding for quite a while now mainly in OO languages such as C# and Java but ...
48
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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?
48
votes
8answers
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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 ...
47
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5answers
5k 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, ...
47
votes
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?
45
votes
4answers
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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, ...
45
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4answers
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Is this a self rolled hashing/obfuscation method? Can you recognize the pattern?

A system we're introducing into the organization is not using any traditional hashing function that I can find. I've been assigned to "approve" it by black-box testing. I suspect passwords are simply ...
44
votes
12answers
7k 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, ...
44
votes
5answers
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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. ...
43
votes
8answers
14k 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
7k views

Can an open Wi-Fi hotspot be considered “secure” when using a VPN connection?

There are many open Wi-Fi hotspots scattered around from cafes to airports. I understand that a non-passworded Wi-Fi leaves traffic unencrypted and therefore available for hackers to read. I also ...
43
votes
6answers
7k 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, ...
42
votes
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 ...
42
votes
7answers
11k 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 ...
40
votes
8answers
6k 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 ...
40
votes
5answers
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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 ...
39
votes
5answers
6k views

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: ...
39
votes
3answers
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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 ...
38
votes
9answers
6k 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. ...
38
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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 ...
38
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4answers
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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?
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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6answers
43k 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 ...
36
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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 ...