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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67 views

Is this symetric or asymetric encryption?

I’m at the beginning of my journey into the world of security. I am reading about the most fundamentals topics and I have encountered something unusual that has thrown me. The Conundrum: I have come ...
2
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1answer
123 views

This is 2015. Has SHA1 been exploited or cracked yet?

went to Qualys SSL lab and tested one web site. One of the findings says the site is signed with weak algorithm SHA1withRSA and I did some research all are saying we should change to SHA-2. may i know ...
0
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0answers
25 views

calculate time for preimage attack (hash creation time is known) [on hold]

Given the 59 leftmost bits of a hash (Cryptographic Generated Address without SEC parameter http://en.wikipedia.org/wiki/Cryptographically_Generated_Address) how fast (on average) will we find another ...
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0answers
58 views

how many sha1 hashes per time on current hardware [on hold]

How many sha1 hashes per second can current hardware (say a 500$ gpu) compute, when the input is 256 byte long? (or any other length). The question behind is how long (or how costly) is it to mount a ...
0
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0answers
33 views

Is it possible to pre populate a password (stored as hashed form in the db)? [on hold]

I think this is a bad practice, but ignore that for now. If I have a login form (username/password and a remember me checkbox). Is it possible to pre populate the username and pwd fields if a user is ...
0
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1answer
56 views

MySQL Database Password protection

I am developing an industry-level web server that requires that all passwords be encrypted in some way. The middle-ware for the server is Java-based. My only restriction is that I can't use API's ...
-3
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2answers
84 views

If I were to perform a MD5 hash every microsecond from 1-1-1970 how many hash colisions would I have [on hold]

I mean with a standard length of 32 you are doomed to have some hash collision, I ask this question just out of curiosity. I havent put a supercomputer or a timemachine just yet.
3
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2answers
637 views

Decoding SHA-512 value

How does the SHA-512 decoder on the following page work? http://md5hashing.net/hashing/sha512#main Hash values supposed to be unable to reverse. Is this page fake?
5
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1answer
63 views

How does combining SHA256 with RIPE-MD160 compare to SHA256 + SHA-3?

Bitcoin stores its addresses as a combined SHA256 + RIPE-MD160 hash. Is it correct to assume this is done to prevent a failure in the algorithm? Since SHA3 was designed to be an alternative to ...
2
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0answers
31 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 ...
2
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1answer
63 views

Hashing algorithm for cryptsetup

I will encrypt my SSD using cryptsetup and I would like to know which hashing algprithm to use. First of all, cryptsetup benchmark: PBKDF2-sha256 262144 iterations per second PBKDF2-sha512 ...
2
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1answer
64 views

Securely storing passwords using PHP5

Starting note: After going through some articles and answers posted on SO related to storing secured passwords I'm still not sure whether my way of thinking is applicable to todays reality. I'm ...
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2answers
55 views

Salt addition in hashing? [duplicate]

I may be wrong here but reading about salt I was wondering whether if we use the same salt for every password saved in our database won't users having same password would lead to same hash even after ...
0
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1answer
70 views

How does PHP's password_hash() BCRYPT cost factor translate into cracking computation times

I am trying to fully understand the relationship between BCRYPT's COST factors and how much more time it would take a machine to crack a password with PHP 5.5's password_hash() The encryption times I ...
0
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0answers
9 views

Does a static salt in addition to a random one add any security? [duplicate]

I'm looking through some old hashing code and found something that made me raise an eyebrow. In order to store passwords, it uses BCrypt to generate a random salt and hash the password. Before that, ...
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2answers
94 views

SHA256 to text or MD5

I want to decrypt a sha256 to text. Is there a way other than bruteforcing to decrypt sha256? Like if I convert that SHA256 to MD5 and then try decrypting?I know its hard and the possible way for ...
3
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2answers
131 views

Is there any reason for using private key 2 times when creating security hash?

One of the payment solutions for the websites provides the following way of creating security hash for payment link: hash = sha1(private_key + payment_params_json + private_key); Is there any ...
4
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0answers
54 views

Random padding in hash functions

In this answer, it was recommended that you add random padding when hashing messages for a trusted timestamp, such as for predictions, in order to avoid dictionary and brute force attacks (at least ...
2
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0answers
51 views

Disallowing Similar Passwords [duplicate]

Upfront, I want to clarify that I am not a professional cryptographer, I am more curious about playing with the math and science behind it, and also want to improve my habits with my own personal and ...
0
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2answers
209 views

How hash ensure integrity of data? [duplicate]

I understand what a hash is, basically we calculate a hash and append it to the message and send it to the receiver. If someone alters the message, the receiver will know because there would be a ...
1
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0answers
35 views

Hashcat Turkish character problem [closed]

I'm using cudahashcat, it haven't special chars like "öçşĞÜ" in standart charsets. I defined charsets with windows-1254 and other encoding types(and -1 öÖçÇğĞşŞüÜıİ?a parameter), i tried but they ...
-4
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1answer
33 views

What is the most secure way to protect a custom CMS from infiltration? [closed]

I have a custom CMS with a randomly generated ASCII 100-character string from this site for both my username/password. I also have this following sha512 encryption system, which was created by ...
0
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2answers
105 views

Is my hashing function good enough

Is there an obvious flaw with this hashing function (written in PHP)? function hash($password) { sleep(1); // Make hashing slow $hash = ""; $iterations = strlen($password); for ( $i = 0; $i ...
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1answer
78 views

Disastrous aftereffects of a hashing attack

I am writing about hashing functions for my thesis. I want to know whether there were disastrous aftereffects of a successful hashing attack in history and what kind of hashing attack was used. ...
1
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1answer
68 views

John the Ripper missing formats [closed]

I have an sha256 hash that I am trying to crack with John the Ripper. However, it doesn't recognize raw-sha256, raw-md5, or any hash format other than descrypt, bsdicrypt, md5crypt, bcrypt, LM, AFS, ...
31
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5answers
6k views

If a web site shows me what my password was changed to, is it stored as plain text?

I just changed the password on a school-related web site. After completing the change successfully, the next page showed what the password was changed to. Can I conclude from this that the password ...
1
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2answers
60 views

Is it known to what message size are standard hash functions injective?

This simple Python script verifies that all messages of length 1 have different SHA-1 hashes: import hashlib s = set() for i in range(256): s.add(hashlib.sha1(chr(i)).hexdigest()) print len(s) ...
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0answers
28 views

Is there any merit to the RFC 3414 (SNMPv3 User Security Model) password-to-key method?

RFC 3414 (published 2002) specifies a method of generating keys based on password in its Appendix, which essentially takes any "passphrase", and keeps on repeating it until there is a 1MB string, at ...
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0answers
28 views

PKCS#7 signed data structure in signed PDF document

Is it mandatory to include PKCS#7 data (OID 1.2.840.113549.1.7.1) octet string into the sequence of PKCS#7 signed data? I mean if you want to sign PDF, you are basically adding PKCS#7 container ...
2
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1answer
45 views

Authenticity of PDF document printed from Word

My MS Word Add-In generates PDF preview of DOCX file on client PC and uploads both files to server. I cannot generate PDF on server. Is there any way to make sure that the PDF is the printed version ...
0
votes
2answers
152 views

Is this the most secure encryption/hashing system? [closed]

I've been doing some research regarding password security and after reading several topics and the Kerckhoff's principle. I came up with what I believe is a really secure system regarding online ...
5
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0answers
187 views

Naive implementation of Rainbow Table and/or Hellman's trade-off

This question is the same one I asked here. Since I haven't got any response or even a comment I will post it here as well. Is there any naive implementation of Hellman's cryptanalytic time memory ...
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3answers
119 views

Is it really necessary to hash user passwords when I already protect my database against SQL injection? [duplicate]

I'm developing a school, I just applied all the SQL injection protections that exist and database security, administrative roles, parametrized queries, sanitize input from the client. But FOOL ME! I ...
2
votes
2answers
129 views

Reducing hash output length [duplicate]

I am using output of (keyed) hash function to make sure the input was not modified, I store it along with input. Now output of SHA-1 is 20 bytes. Say I want to reduce the output. And have it output 10 ...
2
votes
1answer
172 views

How can Alice and Bob prove that they share a file?

Carl asks Alice and Bob if they have a file f such that for a secure cryptographic hash function h, h(f) = K. Both claim to have f, but they can't show the file. Carl doesn't believe them. He can ...
2
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0answers
46 views

How secure is Visual host key, and how is SHA2 converted into that representation?

SHA2 has 256 bits of possibilities. Visual host key seems to have the following upper and lowercase = 26*2 numbers and symbols = 20 Additional symbols = 22 Total 94 characters represented in ...
18
votes
3answers
3k views

Is using the concatenation of multiple hash algorithms more secure?

Is it more secure in practice to use the output of multiple hash algorithms instead of a single one (assuming that the output size is the same)? By secure, in this context, I mean protecting against ...
2
votes
1answer
69 views

What is a key-hardened hash?

I've seen the term 'key hardened hash' used to describe a recommended way to tighten up password hashing. What does this mean? Can it just mean to use a pepper?
2
votes
1answer
139 views

Why do major sites(Facebook, Google, etc) still send passwords unhashed? [duplicate]

QUICK SUMMARY: It seems like modern websites, for security's sake, should all have the client hash their own passwords before sending them to the server, who will rehash them, in order to avoid ...
1
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2answers
73 views

Does recursive hashing weaken properties of a cryptographic hash algorithm?

Specific example of mine concerns the probability of collision, where I have two plain texts A and B that I want to hash using MD5. Given the cryptographic hash function H and the following: A' = ...
4
votes
4answers
103 views

What's to stop someone from just MITMing a checksum?

A lot of sites offer MD5 or SHA sums to verify the validity of your download, but why do some things rely almost entirely on this? Is there anything in place to prevent people from just replacing ...
4
votes
2answers
48 views

Is hashing schema information for client when generating SQL queries more secure?

I'm planning to implement a web system wherein APIs and presentation for CRUD in data tables are automatically generated, like that in phpMyAdmin. How I plan to implement this is to construct SQL ...
1
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1answer
95 views

Is it insecure to hash multiples times?

Hashing multiple times (rounds) seems like a standard practice in password hashing to increase the work factor. Surely, everyone will agree increasing the work factor to compute the password hash is ...
1
vote
2answers
129 views

Is bruteforcing the last character of a salt a good idea?

Would it be a good idea security-wise to store salts with their last character removed, and then bruteforce the last character to further the amount of time it would take to create rainbow tables and ...
0
votes
1answer
118 views

Could overlapping SHA256 hash begin to loop at some point?

I have a system that needs to send a key to the user. This key is used for validation after work and needs to be shown that we do not change it mid-work so we send to the user in the middle of work a ...
4
votes
1answer
276 views

How can I extract the hash inside a encrypted PDF file?

As long as I know, the encrypted PDF files don't store the decryption password within them, but a hash asociated to this password. When auditing security, a good attemp to break PDF files passwords ...
1
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1answer
26 views

Should I verify installer file PGP hash?

Let's say that I'll download an installer for a program on Windows and the publisher has released PGP Signature for the file. The installer file does not have any code signing certificates. If I ...
1
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1answer
53 views

Is it fine to store single-use beta keys plain-text?

Is it okay to store single-use beta keys in plain-text in the database? I'll be pre-generating and storing about 2M keys. The keys get passed around so that people can sign up with it, rather than let ...
5
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2answers
232 views

How is a hash's algorithm detected based on the hash?

I was reading an Ars Technica article this morning and came across the following towards the end (emphasis mine): Equation Group included six other hashes in different exploits that remain unknown ...
4
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1answer
42 views

Why there is a signed hash in Certificate request (.csr file)?

I wonder why there is a hash signed by private key in the CSR? It does prove that I have the private key that belongs to the public key in the .csr. But who cares whether I actually do possess the ...