SHA-1 is a hash function that will soon be two generations old. It is no longer considered secure and should only be used for backward compatibility.
11
votes
1answer
820 views
No SHA-1 Collision? Yet SHA1 is broken?
Is there a known pair of distinct bit strings (A,B) such that SHA1(A) == SHA1(B)?
If the answer is no than how can SHA1 be considered broken?
10
votes
2answers
438 views
Why do we append the length of the message in SHA-1 pre-processing?
As we know, SHA-1 is irreversible, so why do we append the length of the message to the preimage?
7
votes
7answers
662 views
How can I improve a password generation scheme based on a shared secret and URL?
I currently use the following method to generate a different password on every website I have to login:
password = SHA1 ( mainPassword . domainName . number )
...
5
votes
3answers
1k views
SHA1 usage for passwords, alternatives and advantages?
My application can authenticate via openid and oauth (facebook, twitter, etc) and also with its own authentication system. I previously switched hashing from MD5 to SHA1 and during migration I had to ...
5
votes
3answers
913 views
In the SHA hash algorithm, why is the message always padded?
In the SHA hash algorithm the message is always padded, even if initially the correct length without padding; the padding is of the form "1" followed by the necessary number of 0s.
Why is it ...
5
votes
2answers
723 views
What are advantages of using a HMAC over RSA with SHA-1 hashes?
I am currently studying for an exam and this was a previous question:
Give one advantage of using HMACs over using RSA to sign SHA-1 hashes.
My thoughts are that it has something to do with the ...
5
votes
2answers
517 views
Accelerating SHA-1
I have a program where computing SHA-1 is the bottleneck. This is using OpenSSL 1.0.0e on a 2.6Ghz 16-core Opteron where I get about 325MiB/s throughput. (SHA1 here is via Andy Polyakov's x86-64 ...
4
votes
2answers
159 views
Is SHA-1 still practical secure under specific scenarios?
It is conjectured that SHA-1 has been broken from the "research" perspective but no in real world. That is that there is an algebraic attack that explores weaknesses on its algrebraic construction. ...
4
votes
4answers
2k views
Does the SHA hash function always generate a fixed length hash?
I'm using the SHA1/2 family of algorithms for a particular project. I'm was wondering if all the SHA algos return a fixed length hash regardless of the length of the data?
4
votes
2answers
185 views
Is SHA1 secure with such many inputs Z that Z = constant secret X + variable public Y?
Let me ask whether SHA1 is designed to be secure for the following case.
You compute each SHA1 of many strings,for example 1 million, where each string is a concatenation of X+Y ,
where X is secret ...
4
votes
2answers
544 views
128 bit hash with least chance of collision
I'm building a storage system for JSON documents where they are looked up on a 128 bit key. These JSON documents have a timestamp within them, but apart from that are user-entered data. These JSON ...
3
votes
3answers
444 views
Calculating the amount of zero bits to be appended to the message
From FIPS 180-3
Suppose that the length of the message, M, is l bits. Append the bit “1” to the end of the message, followed ...
3
votes
3answers
769 views
Is it fair to assume that SHA1 collisions won't occur on a set of <100k strings
I'm building a system that has to take file paths, and generate a unique name for each one. I'm planning on using SHA1 as the hash function. My question is: do I have to deal with possible collisions ...
3
votes
1answer
129 views
Does hash_df use binary or an ASCII hexadecimal representation for numbers to be passed to the hash function?
I'm implementing the HASH_DRBG algorithm.
As per NIST-SP800 90 document for HASH DRBG Generation, section 10.4.1 "Derivation Function Using a Hash Function (Hash_df)", the Hash_df algorithm contains ...
2
votes
2answers
412 views
Different implementations of SHA1, which one is correct?
I have noticed that different implementations of SHA1 give different results. As I'm currently programming my own SHA1 implementation (in MATLAB / GNU Octave), I wonder which one should I follow?
...
1
vote
3answers
73 views
Is Base64(SHA1(GUID)) still unique like the original GUID?
Basically what the title is; GUIDs are unique by design. If you run the GUID through SHA1 and then Base64 the hash, will the resulting string have the same guaranteed uniqueness as the GUID, or not?
1
vote
1answer
312 views
Crack SHA1 hash code
Given a set of SHA1 hash code, if we knew a portion of the plaintext for each particular hash code, and also the remaining portion of the plaintext is a constant value for each hash code.
Is it ...
1
vote
1answer
253 views
HASH Algorithm for 8 bits MCU
I need to implement the HASH algorithm (MD5 & SHA-1) on an 8 bit MCU. I hear it can only be implemented on 32bit and sometimes 16bits MCU. Is that possible? I will appreciate link where possible. ...
1
vote
0answers
69 views
Is SHA-1 collision free on data up to 20 bytes long? [duplicate]
Is SHA-1 collision free on data up to 20 bytes long (lenght of hash / internal state)? That means that every input produce unique output, but you surely know that, i just write it in order my question ...
1
vote
0answers
31 views
Will length-extension work if secret is not prefixed but appended to the data? [duplicate]
Possible Duplicate:
Why is h(m||k) insecure?
Length-extension allows to append any data to the message while not knowing the secret. Any length-extension explaination one the web considers ...
1
vote
0answers
190 views
Openssl implementation of improved sha1 hashing [closed]
I want to use the improved sha1 hashing algorithm from the Intel blog described here Intel sha1 hashing. Currently I am using Openssl sha1 hashing in my application.
I wanted to know if anybody has ...
0
votes
2answers
148 views
SHA-1:Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output?
Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output? What is the probability that a 160-bit SHA-1 hash output contains at least 128 1's?
0
votes
1answer
69 views
How to take SHA-1 safely for my particular case?
Let me ask about my toy passwords generator program X5 which I want to improve.
X5 uses a secret key and a public key to generate a password.Where any public key is supposed to be known to hackers in ...
0
votes
0answers
34 views
SHA-1: Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output? [duplicate]
Is there any mathematical result that gives us the minimum number of 1's in a 160-bit SHA-1 hash output? What is the probability that the 160 bit result contains at least 128 1's?
0
votes
0answers
50 views
why these specific values used to initialize ipad & opad in HMAC [duplicate]
Possible Duplicate:
What do the magic numbers 0x5c and 0x36 in the opad/ipad calc in HMAC do?
I'm reading the book Network Security Essentials written by William Stallings.
in this book,in ...
-1
votes
1answer
65 views
RSA SHA1 signature from public key
Is it possible to generate signature only from Public key. See example below where i have valid signature but what if I change hash ? Is then any way to do this?
Public key(160 bytes):
...
-2
votes
1answer
170 views
Recovering SHA1 knowing 2/3 of the hash generated
I am doing some research on cryptography, so I generated a random string of numbers resembling a creditcard number(according to MOD10 validation) and encrypted it with SHA1 algorithm for encryption. ...
-4
votes
1answer
250 views
finding collision for truncated SHA1 hash output
Suppose we truncate only 40 bits of sha1 hash output.hence it is insecure.how can we find two message as input which gives first 40 bits of hash as same value i.e we have to find collision for first ...
