A hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm tries to make it difficult to predict the output for a given input, find two inputs with the same output, or reconstruct the input from the output.

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How can I make sure password hashing is secure on computers while not being prohibitively slow on mobile devices?

I'm new to cryptography and its implementations. I'm designing an Android app where an user enters a password to retrieve some encrypted data. After some research on possible solutions I ended up with ...
3
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2answers
409 views

Is there any way to cryptographically hash a human thumbprint?

Is there any way to cryptographically hash a human thumbprint into a form that can be consistently reproduced by thumbprint readers? Assuming that it would be possible to create a database of ...
32
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HMAC - Why not HMAC for password storage?

Nota bene: I'm aware that the good answer to secure password storage is either scrypt or bcrypt. This question isn't for implementation in actual software, it's for my own understanding. Let's say ...
9
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2answers
779 views

Does it make sense to choose a longer password than the output of a hash?

Let's take MD5 for example: It outputs a 128-bit hash. Does it make sense (in theory) to choose an input (password) which is itself longer than 128-bit? Does it increase the probability of a ...
3
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2answers
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Finding out whether a website uses unsalted MD5 for password hashing

I'm working on a project where websites are analyzed and rated according to password security (factors like min/max password length, alphabet size and more are then calculated into a score). A great ...
8
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4answers
765 views

How can we factor Moore's law into password cracking estimates?

How would we go about factoring Moore's law into exceedingly long password cracking estimates? Let's say we've got a 12 character password containing mixed-case alpha characters and numbers, i.e. ...
6
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3answers
325 views

Would secure storing of past used/generated passwords be a good idea?

Let's assume an organisation that generates ~100 Passwords a week; these Passwords are 32-Characters long and randomly generated. The consultants that need passwords generated use a Password-generator ...
1
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2answers
277 views

How can I generate a unique SALT for multiple apps sharing one user database?

Let's say that I have one Database, and several separate web applications that share the database. If hashes are to be unique and generated on the server-side, how can I ensure that I am generating a ...
3
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1answer
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Hashing passwords before inserting into database

For the last 2 weeks I have been reading many blogs about website security and hashing passwords. Many sites have mentioned the pro's and cons about different ways of doing this, which has left me a ...
6
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169 views

Is it safe to store hashes of possibly non-existing passwords in a less safe way?

I would like to implement a lockout mechanism that not only protects against same username and many passwords attacks, but many usernames and same password attacks too. To implement this I figured I ...
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What is the purpose of a Pepper?

I've been trying to find out exactly what a pepper is. The only things I could accurately determine are that a Pepper: Is theoretically unique from site to site and hard-coded in the site's source ...
3
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5answers
406 views

Are hash functions “strongest link”?

It seems to me that if you were to use multiple hash functions, the "strongest link" would hold up the others. For example: HelloWorld --- md5 --> 68e109f0f40ca72a15e05cc22786f8e6 --- sha256 ...
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Devising encryption schemes and protocols

I am wondering how encryption schemes are developed and why certain decisions are made. For example. I have seen a company hash a string with SHA1 and then RSA encrypt it. Why? I've also seen the ...
0
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2answers
3k views

how to know what hash function have been used

I have a hashed password and the plaintext password and i want to know the exact algorithm that's been used. I have the input and the output of the hash/encription algorithm. How would I know what ...
2
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3answers
774 views

Password Security and ocl-Hashcat-plus

I recently read the Ars Technical Article about new features in ocl-Hashcat-plus. In light of questions like: Long Passwords: How are they more secure? and XKCD #936: Short complex password, or ...
2
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4answers
421 views

Why do some passwords not allow certain types of characters?

Is there any programing related reason why some password cannot have certain characters? If the idea in storing a password is to store it's hash, since a hashing function can take any input (ok at ...
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1answer
425 views

Is double hashing bad? [duplicate]

I hear rumors that double hashing is bad... like hash("sha512", hash("whirlpool", "string")) Is it bad and less secure? if so why? Thanks for any help!
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4answers
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Using only password to authenticate user (no “username” field)

I am creating a client access system, to allow manage invoices, make payments, access information about their products and information/functionality alike. Supposedly there are less than 1000 ...
7
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2answers
653 views

Salt placement prior to one-way hash

In one-way hashing its common to prepend or append the salt to the secret and then hash it: (salt + secret) or (secret + salt). I was thinking of this metaphor as salt falling on a plate of food. It ...
11
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4answers
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How secure is the SRP that Blizzard uses to protect passwords?

Blizzard very recently announced that their network was compromised, but they assure users in their statement that the password information that the attackers had access to was saved in a secure way: ...
0
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3answers
422 views

Need references about why public access to a password hash and salt is poor practice

What are some published industry standards about why revealing the password hash and salt are poor or bad practices from a security perspective? I am dealing with a vulnerability where anyone can ...
2
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3answers
418 views

Is there any reason I shouldn't use SHA1 of salt + website name + master password for my password in websites?

I considered writing a program to do the above for websites I only intend to use for short-term use.
6
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3answers
13k views

Generating an unguesable token for confirmation e-mails

I'm generating a token to be used when clicking on the link in a verification e-mail. I plan on using uniqid() but the output will be predictable allowing an attacker to bypass the confirmation ...
2
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1answer
340 views

Unknown encryption string [closed]

I'm trying to learn about encryption and decryption methods when I faced this string: {MD5}JfnnlDI7RTiF9RgfG2JNCw== MD5 is 16-byte string, so anyone know what type of encryption is this and why ...
3
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2answers
639 views

Is mt_rand() suitable for generating a salt?

Assumed I have to following code in order to generate a random blowfish salt for saving a new password: $blowfishCharacters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789./'; $salt ...
18
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1answer
319 views

What's this kind of authentication scheme called?

In the past I've heard about a scheme to prove your identity online in places like forums, without having to create an account. When posting, the user would enter a password which is then heavily ...
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718 views

User password as key instead of hashing it

I was reading here on Hashes and Salts and I thought about another method to do user authentication. I need your thoughts on this as I might be overlooking something. Scenario: For web application ...
8
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4answers
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SHA-512 unix passwords. How secure are those hashes, really?

I came across this very alarming sounding thread which indicates a GPU with about half the compute capacity of the GPU currently powering the monitor I type this on is capable of 11.5k c/s. I'm not ...
2
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1answer
2k views

How to save the random salt to the database

As I understand it, salting and hashing passwords is the way to go. I also understand that to authenticate a salted and hashed password, the random salt needs to be saved. Does this mean that if I use ...
5
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5answers
971 views

Is it a good idea to use an input by the user as SALT?

I have read many Q&As here on IT Security about password hashing and salting. I am building a simple registration form for our community website which will be used by our members to create their ...
5
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2answers
204 views

What is the meaning of the term “simple string” for the SALT string in Unix crypt using SHA-256 and SHA-512?

In Unix crypt using SHA-256 and SHA-512 the author, Ulrich Drepper, introduces the SALT string as the following (highlight by me): For the SHA-based methods the SALT string can be a simple string ...
4
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2answers
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Rounds of MD5 and SHA512 Hashing Algorithms

What is the exact number of rounds employed by the MD5 and SHA512 hashing algorithms? According to various sources, the SHA512 hashing algorithm employs a total of 80 rounds ...
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3answers
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What's the use of making users use digits, uppercase-lowercase combination password if the passwords are hashed?

Some websites, even the StackOverflow asks for atleast 1 digit, 1 uppercase character in the password. Does this really matter when the developer uses a password-hash algorithm to store the passwords ...
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1answer
380 views

Generate Keytool Object from CSR

I have to develop an application which uses another application for generating a CSR. After generating the CSR I have to provide this CSR along with a SHA256 hash of the public key to a CA. The ...
7
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4answers
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when people say a file has a checked md5 hash, what exactly does that mean?

ok I was just reading this site: http://www.zdnet.com/blog/bott/stay-safe-online-5-secrets-every-pc-and-mac-owner-should-know/3542?pg=4&tag=mantle_skin;content and thought of something I always ...
36
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3answers
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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 ...
8
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3answers
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How exactly is MD5 vulnerable to collission attacks?

I've often read that MD5 (among other hashing algorithms) is vulnerable to collisions attacks. I understand the collision part: there exist two (or more) inputs such that MD5 will generate the same ...
0
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1answer
624 views

What does it mean by the 'Hash of a malware'?

I have just recently started to delve into the topics of malware. In my hunt for malware binaries, I came across certain responses that it is not easy to grab binaries based on malware names like ...
2
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1answer
2k views

How do I generate a blowfish password hash in Ubuntu?

What's the command line to generate a blowfish password hash? I can't seem to figure this out at all. Apache's htpasswd only supports bcrypt, and openssl passwd doesn't even do blowfish hahes (but it ...
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6answers
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Tracking unique web site visits without logging IP addresses

On Monday, some IP address xxx.xxx.xxx.xxx visits my site. I log it. On Tuesday, another IP address yyy.yyy.yyy.yyy visits my site. I log it. If the two IP addresses are equal, I throw out the ...
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2answers
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How to get an NT hash from registry? [closed]

I want to manually get the NT hash from the registry (without any tool). Let's say just for the administrator. I know that it must be stored in the SAM area of the registry somewhere so I tried to ...
47
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3answers
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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 ...
2
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3answers
2k views

Reversing Password Hashes [duplicate]

if someone got hold of the hashes of all passwords for a website, how do they 1) get passwords from the hashes. As far as I can tell from searching the internet everything seems to say do a dictionary ...
9
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1answer
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HKDF and key stretching

I thought that all key derivation functions would do a key stretching phase, by iterating some kind of process. But I can't see that process in HKDF. HKDF doesn't do key strengthening? If I have a ...
2
votes
5answers
380 views

Methods used to reverse a hash

I know that a hash is a one-way-function and that therefore there isn't a reversal function. By reversing a hash I just mean to find some plaintext that gives the hash. I think that I understand that ...
2
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1answer
2k views

What are realistic rates for brute force hashing?

I'm trying to gauge password strength assuming that the attacker has a hash of my password. Can anyone cite some realistic contemporary rates at which someone could perform various hashes? I know most ...
2
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3answers
658 views

Storing passwords on a home computer

I remember all the passwords (and variations of passwords) that I use for various sites online. The problem is not that I forget a password, but that I forget which password goes with which site. And ...
3
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2answers
114 views

How to ensure two messages are from the same party

I need to verify that two messages, that came over distinct channels, come from the same origin: without knowing anything about the origin beforehand the channels are one-way, only one message may ...
10
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2answers
16k views

Safety of publishing last 4 credit card digits in age of fast computing?

How safe is it to make public the last four digits of a credit card? Credit card numbers have a specific format. Digits tell you what type of institution issued the card, what bank issued the card, ...
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1answer
465 views

After salting my passwords, are they protected against dictionary attacks? [duplicate]

I use sha1() to hash my users passwords, but recently a friend told me that if someone get the hash then they could use dictionary attack and he recommended using salts. I implemented a random salt ...