Questions tagged [sha]

Secure Hash Algorithm is a family of cryptographic hash functions published by NIST. This includes SHA-1, and the SHA-2 and SHA-3 families of functions.

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88
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80k views

What is the relationship between "SHA-2" and "SHA-256"

I'm confused on the difference between SHA-2 and SHA-256 and often hear them used interchangeably (which seems really wrong). I think SHA-2 a "family" of hash algorithms and SHA-256 a specific ...
73
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4answers
186k views

Is SHA1 better than MD5 only because it generates a hash of 160 bits?

It is well known that SHA1 is recommended more than MD5 for hashing since MD5 is practically broken as lot of collisions have been found. With the birthday attack, it is possible to get a collision ...
69
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3answers
11k views

Why is Google still using a sha1 certificate on its own site when they are phasing them out in Chrome?

Firefox dev tools shows that https://www.google.com is using a certificate signed with SHA1. Why is Google doing this when they are phasing out the certificate themselves? Shouldn't this only hurt ...
65
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1answer
7k views

What are the implications of a SHA-1 collision being found?

Google have announced the discovery of a SHA-1 collision between two PDF files with distinct content. While SHA-1 hashes are no longer permitted for SSL/TLS certificate fingerprints, and other ...
56
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5answers
8k views

Is using bcrypt on existing SHA1 hashes good enough when switching password implementation?

I'm working on improving a CMS where the current implementation of storing password is just sha1(password). I explained to my boss that doing it that way is incredibly insecure, and told him that we ...
47
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3answers
4k views

Is Git crowdsourcing cryptographic attacks?

A strong cryptographic hash makes collisions unlikely. Many cryptographic protocols build on that fact. But Git is using SHA-1 hashes as object identifiers. So there are a lot of already computed ...
44
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3answers
6k views

How safe are signed git tags? Only as safe as SHA-1 or somehow safer?

How safe are signed git tags? Especially because git uses SHA-1. There is contradictory information around. So if one verifies a git tag (git tag -v tagname), then checksouts the tag, and checks that ...
36
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5answers
6k views

Should I trust a website which uses a SHA-1 HTTPS certificate?

I am on a website where I need to pay for something. This website has the following warning in the top left: This site uses a weak security configuration (SHA-1 signatures) so your connection may ...
34
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4answers
5k views

Does every hash value have an inverse value?

There are many different hash functions, md5, sha, and others. They take a value V and produce a H via transformation Function(V) = H, where Function is md5, sha, etc. My question is: Does every hash ...
29
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3answers
39k views

Are there any known vulnerabilities in PPTP VPNs when configured properly?

PPTP is the only VPN protocol supported by some devices (for example, the Asus RT-AC66U WiFi router). If PPTP is configured to only use the most secure options, does its use present any security ...
28
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4answers
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How secure is this hash-based personal password scheme? [duplicate]

I use a password scheme where I keep a small number of easy to remember personal passwords. Instead of using the passwords directly for each service, I run them through a hashing algorithm first, as a ...
27
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7answers
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Is sha1sum still secure for downloadable software packages signature?

We use sha1sum to calculate SHA-1 hash value of our packages. Clarification about the usage: We distribute some software packages, and we want users to be able to check that what they downloaded is ...
25
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3answers
13k views

Is SHA1 weak for SSL?

I noticed that today after I scanned a site on the Qualys SSL Labs site that SSL ciphersuites which use SHA1 are now highlighted as being "Weak". It seems this has just happened; I scan sites pretty ...
24
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4answers
5k views

Does Rehashing a weak hash with a strong algorithm make it strong?

Imagine the following situation. We're making a web application which should be really safe Now the accounts/users are not directly added by us but they receive a letter with a logincode. We get a ...
23
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9answers
29k views

Deprecation of SHA1 code signing certificates on Windows

EDIT (7/7/2016) - see addition at the end of post I have been keenly following the issues with regards to Microsoft deprecating the use of SHA1 code-signing certificates for Windows executables (http:...
21
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6answers
32k views

Reversible Hash Function?

Is there any reversible hash function? The hash function like SHA and MD5 are not reversible. I would like to know if there exist some reversible hash functions?
21
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2answers
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How secure is BCRYPT(SHA1(Password)) [duplicate]

This question is a fork from a previous question here: Is it safe/wise to store a salt in the same field as the hashed password? Assume you run a web portal, and store passwords in SHA1 hashes. How ...
19
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1answer
8k views

What's the hash for in ECDHE-RSA-AES-GCM-SHA?

Presumably the SHA is for deriving the AES key from the shared secret. Where else is the hash used? ECDH just does ECC (no hashing). RSA does masking and padding but this doesn't involve the ...
18
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4answers
4k views

Have weaknesses in SHA-1 and MD5 ever actually been successfully used in an attack?

Pretty much every guide, how-to, and reference for dealing with passwords and hashing has a warning in big or bold letters stating something along the lines of: SHA-1 and MD5 are NOT secure and ...
16
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2answers
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What are SHA-rounds?

I understand more sha-rounds make it difficult to bruteforce the hashed password in /etc/shadow. Higher rounds also use more CPU processing when executing sudo commands and logging into the Unix ...
15
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3answers
2k views

Trying to understand why signatures in root certs "are not used"?

Taken from here: Don't worry if the root certificate uses SHA1; signatures on roots are not used (and Chrome won't warn about them. Why are the signatures not used? Are not root certificates ...
15
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1answer
21k views

Firebug reports SHA-1 certificate error

For the script at the bottom of this post, Firebug reports the following error: This site makes use of a SHA-1 Certificate; it's recommended you use certificates with signature algorithms that ...
15
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2answers
2k views

How does SHA3 (Keccak & SHAKE) compare to SHA2? Should I use non-SHAKE parameters?

Keccak is the winner of the SHA3 competition. Since Keccak is highly customizable (presumably for security/memory/time/speed tradeoffs) there does seem to be some controversy around how Keccak ...
14
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2answers
6k views

Why should I choose SHA (such as SHa-512), instead of bcrypt or PBKDF2, for FIPS-compliance?

Due to regulation, my company needs to be FIPS-compliant. I was looking at the current list of FIPS-approved cryptographical methods and I notice that neither bcrypt or PBKDF2 are in this list. Does ...
14
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3answers
15k views

With ASIC bitcoin miners, should SHA256 be considered insecure for password hashing?

I'm sure everyone here has seen the rise and further rise of bitcoin. The process used for mining bitcoin is basically "let's brute force an SHA256 hash that is less than this amount" That being ...
13
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1answer
8k views

Should SHA-1 be used with RSA-OAEP?

PKCS#1 defines SHA1 as a default hash function and all implementations support this hash function and the mask generation functions based on SHA1. In some implementations you can change the hash ...
13
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1answer
2k views

Torrent "bad seed" attack by Sony, how does it work?

Sony recently saw a large amount of data stolen. In order to prevent the stolen data from being spread using torrents, they are doing what was called a bad seed attack. What is this attack? Is this a ...
12
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4answers
20k views

Is sha-1 hash always the same?

Is it possible to ensure that a string is hashed always the same way no matter which language you use to do it (Java, vb.net... ) and no matter what operative system you are?
12
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4answers
15k views

HMACSHA512 versus Rfc2898DeriveBytes for password hash

We are currently using HMACSHA512 in .net, with a 128Char (64byte) validation key The salt is 64 char randomly generated string. We allocated 2048 length on the database for the hashed base64 string ...
12
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5answers
2k views

How did the Shattered.io group manage to create a SHA1 collision for a PDF that is similar looking to the original?

So I've been trying to understand what a SHA-1 collision is and what it means but there's one thing I'm not quite understanding. How did they manage to not only find two documents with the same hash -...
12
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3answers
11k views

What does GUID have, that a Whirlpool, MD5 or SHA-2 hash don't?

I'm trying to understand the use of GUID and what has always left me wondering is what's so special about them that I should consider using them instead of rolling my own type of unique ID. In other ...
12
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3answers
6k views

Should we be using SHA3? (2017)

This question is a duplicate, however I feel that it's necessary given the question. The original was posted in 2012: about 5 years ago before NIST had even published the final specification. The ...
12
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3answers
1k views

How will SHA1 deprecation affect internal CA's?

I am hearing that the SHA1 Deprecation notices from MS/CHROME only apply to certs that are a part of a public trusted root program. This makes one believe that IE will have new logic built in to allow ...
11
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2answers
930 views

Password generation - too primitive?

A while ago (12 years old), I recognized my passwords weren't safe at all. Because I used the very same password everywhere, some grumpy admin could easily take over all my accounts (he got mail and ...
11
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2answers
5k views

“Official statement” on php.net : CRYPT_BLOWFISH is strongest hash algorithm. Why?

First: I asked this question on stackoverflow and was kindly asked to post this here again. See the original question here. According to the [early] doc pages of the new PHP 5.5 password hashing/...
11
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2answers
26k views

Obsolete cryptography (SHA1) warning although certificate uses SHA256

I ordered a certificate with SHA256 from Comodo and was wondering why Chrome shows this message: Your connection is encrypted with obsolete cryptography. The connection is encrypted using AES_256_CBC,...
10
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4answers
4k views

SHA & MD5 Collisions for shorter strings

This is not for passwords. I understand that MD5 and SHA-512, etc... are insecure because they can have collisions. However, is it still possible to have a collision if the string length is less than ...
10
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3answers
19k views

Why do most hashing functions produce hashes that have characters a-f 0-9?

This is something I never understood about hashing functions. I know that algorithms like whirlpool and blowfish both produce outputs that don't follow this pattern, but why is it that most do? Is ...
10
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3answers
4k views

SHA and "Bits of Security"

I've researched several forms of encryption/hashing and have often come across the term "bits of security". For example, at least one source claimed SHA-256 = AES128 = ECC256 = 128 bits of security. ...
9
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3answers
15k views

Is it required to have the same Domain Name and Common Name for SSL Certificate?

I have an SSL cert in which CN is "abc.xyz.com". But the url shared to 3rd party organization to access a web app on our server is: "def.stu.com/what-ever". When this arrangement is working for ...
9
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2answers
7k views

Can I use SHA-512 hash as AES key?

I want to combine hashing and encryption for better security. So can I use a hash key generated from SHA-512 as a key in AES. For example, I have a password "secret", I calculate SHA-512 hash for it ...
9
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2answers
1k views

Will Google block HMAC-SHA1 along with SHA1 signed certificates?

So, right now, there is a push for moving from SHA1 signed certificates to SHA256 signed certificates by Google. My understanding is that you cannot use SHA1 for signing certificates but HMAC-SHA1 can ...
9
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2answers
23k views

How to reverse engineer password from /etc/shadow

I failed to answer a question in a CaptureTheFlag event, and the the question still bugs me. I want to share the question here and please help me if you know the solution. Question: You have the ...
8
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6answers
12k views

Is there a table that compares hashing algorithms by speed, relatively (machine independent)

As far as I understood*, one of the major criteria when choosing a password / salt hashing algorithm is it's speed. To prevent brute force attacks, a slower algorithm is better (and also makes it more ...
8
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3answers
64k views

Why does MD5 hash starts from $1$ and SHA-512 from $6$? Isn't it weakness in itself? [duplicate]

I have moved this question from stackoverflow to this place. I know it may be a question about 'opinion' but I am not looking for a private opinion but a source of the final decision to keep it this ...
8
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2answers
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Why is it fine for certificates above the end-entity certificate to be SHA-1 based?

I have heard about the phasing out of SHA-1 based certificates for end entity use, and the steps that are outlined for Google Chrome to display progressively more aggressive warnings for SHA-1 ...
8
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2answers
923 views

Why is weakness of SHA-1 considered a threat to TLS security

If I understand correctly the role that a hashing algorithm (e.g. SHA-1) plays in TLS certificates is as follows: The hashing function is applied to a subject's public key. The CA then uses their ...
8
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2answers
647 views

Does randomness prevent collision attacks?

Google have recently announced a practical SHA-1 collision. A few years ago MD5 had similar issues and researchers even created a fake CA. This would not be possible today - even with MD5 - because ...
7
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3answers
4k views

Why not just use a small but unusual number of hashing rounds?

When it comes to hashing passwords, it is nowadays practice to do 100'000 or 200'000 iterations of SHA256/SHA512, or at least something in that ballpark. But my question is, why is it not safe enough ...
7
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4answers
7k views

Store password using sha1 [duplicate]

I've been using the sha1() function to hash password before inserting it into my database. But I have this procedure so that it just won't be the password to be hashed. My page would register a user ...

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