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Should I be concerned if the "FBI" has logged onto my Ubuntu VPS?
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295 votes

An IP address can be set up in DNS to resolve to any host name, by whoever is in control of that IP address. For example, if I am in control of the netblock 203.0.113.128/28, then I can set up 203.0....

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SSH - If Eve has the passphrase and public key, can she derive the private key?
50 votes

The private key is unrelated to the passphrase. So is the public key. The public key is also generally stored unencrypted, even when the private key is protected by a passphrase. (Exceptions may exist ...

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Cryptography that looks like ordinary email
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44 votes

Say what you actually want to do is to make your encrypted email look like spam. OK, how to accomplish that? One possible way would be to take the ciphertext and break it down into managable chunks ...

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Encrypting a few TB of Data
41 votes

I find some of your comments curious. Particularly, I'm trying to stay away from methods that are reliant on an application, and do it manually - as I'd feel more in 'control'. and I don't need ...

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Convert SHA-256 to SHA-1 and MD5 - Increase bit length/entropy?
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24 votes

And it is longer than the input string, with 288bit instead of 256bit. So did we actually increased the entropy? No, you did not increase the entropy. In this context, "entropy" basically refers to ...

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Recommended level of password complexity for Keepass
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19 votes

Let's first establish clearly what should be a common sense truth: A password manager master password is a very high value secret. (This is irrespective of which password manager you are using.) This ...

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What does EIP stand for?
18 votes

One of the basic things that a computer needs to keep track of is where in memory are located the instructions currently being executed. This is normally done by the CPU using what is often known as ...

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Is there a common best practice for naming public and private PGP keys when exporting them?
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16 votes

While obviously it's very hard to prove a negative, I think that the reason why you have found no such "common best practice" is that none exists. The key itself doesn't care about its file name. ...

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Why is it dangerous when an attacker can control the `n` parameter to `memcpy()`?
15 votes

A good answer has already been given by sasha, but I want to look at this from another angle; specifically, what memcpy actually does (in terms of what code gets executed). Allowing for the ...

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Why is STARTTLS used when it can be downgraded very easily?
14 votes

Downgrade attacks are active attacks. Active attacks are much easier to detect, and are typically more difficult to perform, than their passive counterparts. Opportunistic encryption, such as optional ...

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How do I check that users don't write down their passwords?
13 votes

First off, I agree with the answers that say that this is a bad idea for a variety of reasons. Second, it appears that you are trying to use technology to solve a human problem. It is very, very rare ...

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How to store passwords written on a physical notebook?
12 votes

Use a mask. No, seriously. Use something like medium-thickness cardboard, obtainable from office supply or hobby stores, to create a rigid grid mask, maybe 30x6 character slots in size, and cut out ...

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Why is some meta data not encrypted in Proton Mail?
11 votes

As already discussed, Proton Mail uses OpenPGP (RFC 4880). OpenPGP traces its roots to the original Pretty Good Privacy, written by Philip Zimmermann in 1991. At that time, while Internet (SMTP) e-...

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ProtonMail security concerns
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11 votes

However, the server must store some form of the mailbox password so that the user can be authenticated. Should a security breach occur on the server, wouldn't it be just a matter of time for a ...

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Self-signed certificate for a IdP-initiated SAML SSO
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11 votes

TL;DR: Self-signed certificates are fine, and even recommended at least in some contexts. Use long validity times to avoid key rollover problems, and if RSA, use at least 2048-bit keys. SAML 2.0 ...

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What's the chance of two PGP keys being exactly identical?
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11 votes

If we assume that your random number generator isn't completely borked, then what's the chance of two PGP keys being exactly identical? can be answered with approximately something raised to the ...

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Why do people think that this is bad way to hash passwords?
10 votes

Aside from what has already been pointed out in the other answers so far, it seems to me like you have a fundamental misunderstanding sitting there right in your question. The output space of a 128-...

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Am I affected by the Intel AMT/ISM/SBT escalation of privilege vulnerability?
9 votes

Based on Matthew Garrett - Intel's remote AMT vulnerablity, which is among the most reasonable (in terms of amount of hyperbole) articles I've seen so far, you can only be affected if your system ...

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Is firefox disabling of insecure TLS fallback part of the HSTS spec?
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9 votes

HSTS, the HTTP Strict Transport Security mechanism, is defined by RFC 6797. The relevant section is section 12.1, No User Recourse, which states (in part) that (my emphasis): Failing secure ...

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Is an 80 bit password good enough for all practical purposes?
8 votes

It has been stated (for a reasonably authoritative source, see Passphrases That You Can Memorize — But That Even the NSA Can’t Guess on The Intercept) that the NSA is capable of (at least) "one ...

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Is it safe to store my passwords in a text document protected by a password?
8 votes

For modern versions of Word (Word 2007 and later), it appears that Microsoft has got the encryption pretty much right: They use multiple iterations of SHA-1 (since Office 2013, this has been replaced ...

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How to see when a HSTS domain is about to expire?
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8 votes

HSTS data is kept by each web browser. When a request is made to a domain that implements HSTS, the response headers will contain a Strict-Transport-Security header that notes the maximum age of the ...

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Is there any way to determine the location of a laptop based on its MAC address or serial number?
8 votes

If I have the MAC address and S/N of a Lenovo 3000 Laptop, is there some way for me to find exact street location of this laptop ? No, there is not. You can get somewhat along the way if you pre-...

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How do I know my tools aren't compromised?
7 votes

One of the articles you link to -- If the NSA has been hacking everything, how has nobody seen them coming? -- makes an assumption in posing the question: "If the NSA was owning everything in sight ...

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Why not use larger cipher keys?
7 votes

In a way, algorithms using such "insanely large" keys already exist. It's called one-time pads. Nobody really uses them in practice, though, since they require a key the length of the message you wish ...

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Can an attack that does not change the server state be considered a CSRF attack?
6 votes

The "state" of the server, in the case of a Bittorrent client, at least includes the list of pending, current and finished downloads, any data related to those downloads, and any settings related to ...

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In PGP how can I be sure about the public key?
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5 votes

Actually, the naiive approach of just grabbing a key from a keyserver isn't vulnerable so much to a man-in-the-middle attack as to a poisoning attack. In a poisoning attack, an attacker provides an ...

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browser can visit the url but other application can't
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5 votes

My question is why can a browser can connect to it A browser will connect over TCP, by default to a port that is normally open on a web server. Web servers normally use port 80 (plain-text HTTP) or ...

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Is encryption key length limitations by governments norm?
5 votes

Permission limit for Encryption is 40 bit key per length in RSA algorithms This is totally nonsensical. First some history: There was a time when key lengths were commonly restricted, particularly ...

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Is signing an encrypted PGP message redundant?
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5 votes

In cryptography, signing and encrypting are orthogonal. Encrypting data provides confidentiality: (ideally) only the intended recipient will be able to gain access to the plaintext. Modern message ...

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