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.

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What does OIW stand for

There seem to be many OID's that have been put in the ASN.1 tree that have the following ISO identified organization: OIW. One example is SHA-1 (ElGamal seems to be another): ...
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206 views

SHA1 no longer considered secure for SSL Certificates — what about Cipher Suites?

Many browsers and Internet companies have recently claimed that SSL Certificates with a signature algorithm of SHA1 will imminently no longer be considered secure. Most notably, Google and Google ...
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40 views

Deprecation of RSA-SHA-1 in DKIM keys?

I recently noticed that OpenDKIM on my mail server is objecting to DKIM signatures from a client, saying their key is insecure. It may be that that's due to lack of secure DNS (confirmation anyone?) ...
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109 views

SHA-1 collision resistance

I'm researching on the SHA-1 algorithm and looking for reasons why it has fallen prey to differential cryptanalysis. I have read the research papers by Merc Stevens and Wang both of which describe how ...
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194 views

Are there valid attacks on full SHA-1?

Google today announced they are sunsetting SHA-1. Its fine by me. But that made me realize I am not keeping up with the research on SHA-1. The Wikipedia page only says Stevens' attack is the most ...
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601 views

A patched SHA1 attempt for password verification

This is a classical scenario: For our web based authentication platform we have a username and a password field. User enters these values and presses Log In. The browser gathers the user data, ...
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740 views

How is SHA1 different from MD5?

On the surface, SHA1 and MD5 look pretty similar. Their diagrams include chunks of bits, bit rotation, xor and special functions. Their implementations are roughly the same length (at least the ones ...
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116 views

Is HMAC-SHA-1 secure?

Although SHA-1 theoretically has collisions, HMAC-SHA-1 which is based on SHA-1 is still widely used (in TLS for example) and is considered to be secure. How is that possible?
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37 views

Calculating IHVs from known message and hash output

Here is a somewhat silly and atypical problem I am currently facing. Usually, when it comes to hashes, one is bothered with finding collisions and preimages. My problem is, I need to find the IHV used ...
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145 views

generate hash of all handshake messages for verify data (DTLS)

I am trying to create a DTLS client finished packet, where I need to generate verify data for handshake hash is need. And here I want to know how to generate handshake hash. As of now I am doing like ...
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132 views

SHA1 collision event probability after n iterations

There are String1 and String2 - some variables-strings. The probability of collision for different ...
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48 views

SHA1 multipart calculation

Is it possible to combine SHA1 digest values to get the SHA1 of the concatenated parts ? I know the "S1" SHA1 of "part 1" and the "S2" SHA1 of the "part 2" and I would like to know the SHA1 of the ...
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102 views

How (in)secure is a signature based on DSA with DSS1 (SHA1) in reality?

As I found out the OpenSSL implementation provided by PHP (openssl_sign) only allows DSS1 as the hashing algorithm for DSA signatures (see also my related question). I’d prefer DSA over RSA in my ...
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51 views

What are the two parts of SHA1's compression function called?

SHA1's compression function has two distinct parts: one where 16 words are expanded into 80 words, and one where the 80 words are used over 80 rounds. Are there specific names or terms for each of ...
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173 views

HMAC-SHA1 vs HMAC-SHA256 for data storage

Reading the question “HMAC-SHA1 vs HMAC-SHA256”, I figured out that the known attacks on SHA1 don't apply to its HMAC version. So, HMAC-SHA1 is quite strong right now. In a protocol like SSL, if it ...
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133 views

Constants Differ in SHA1 implementation

I am trying to understand why the constants differ in this SHA1 implementation: https://code.google.com/p/crypto-js/source/browse/tags/3.1.2/src/sha1.js ...
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3k views

HMAC-SHA1 vs HMAC-SHA256

I have three questions: Would you use HMAC-SHA1 or HMAC-SHA256 for message authentication? How much HMAC-SHA256 is slower than HMAC-SHA1? Are the security improvements of SHA256 (over SHA1) enough ...
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2answers
643 views

Is PBKDF2-HMAC-SHA1 really broken?

I just read through this article which demonstrates practical (and seemingly trivial) collisions in PBKDF2-HMAC-SHA1, and provides a few examples of collisions. Am I missing something here? Is ...
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1answer
263 views

Why does Openssh use only SHA1 for signing and verifying of digital signatures?

I am learning SSH protocol. With my current understanding of SSH protocol, I think that message digest algorithms for using in digital signature should be derived from Key Exchange. But Openssh ...
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172 views

What is the best way to share a shared secret key over HTTPS to be used for HMAC authentication?

I am writing an application in Java that will be using SHA-1 HMAC message authentication. From what I understand, a connection over HTTPS is considered secure enough to share a secret key in plain ...
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2answers
159 views

Best way to get 32 bytes from PBKDF2

Use the PBKDF2 output as an HMAC key, hashing two different inputs - once for 20 bytes and once for 12 : ...
3
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1answer
166 views

TLS: Is Integrity assured when using NULL cipher

In specific implementation we're using TLS 1.0, open ssl 0.9.8 but i'm referring to RFC 5246. For performance reasons, I'm being asked if we can use TLS without encryption. The hope is that the ...
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47 views

Digital Signature with Encryption

Hope it will be clear. I need to digitally sign pieces of information. What I'm currently doing is the following (for each piece of information): Run SHA1 on the information Encrypt the result with ...
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1answer
148 views

Increased security weaknesses when truncating SHA1

Given the following preconditions: A plaintext A (~512bit length), that is hashed by using SHA-1 and truncated to (the first) 64 bits. I know both, the plaintext and the truncated hash, and want ...
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236 views

Convert a number to sha-1

I have a task to find a the message for which the SHA-1 hash's last 11 symbols in hexadecimal presentation corresponds to an 11-digit number. I have been given the following example solution: For ...
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1k views

What does AES256-CTS-HMAC-SHA1-96 mean in relation to Kerberos?

I'm not completely clueless as to what it means, but I'd like to understand it at a higher level. The highest encryption type used by Active Directory domain controllers for Kerberos authentication ...
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365 views

Why are the initial states of hashes functions (like SHA-1) often non-zero?

There is already a question asking "Why initialize SHA1 with specific buffer?" and my question follows on from this: Why are the initial states of hash functions often non-zero? For most, I have ...
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169 views

Can you get two unpredictable hashes from the same message with, e.g. SHA1?

I'd like to create a database of questions and answers so that an attacker with access to the database can't obtain either the questions or the answers. If H0 and ...
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456 views

Why initialize SHA1 with specific buffer?

SHA-1 is initialize with a specific buffer: h0 = 0x67452301 h1 = 0xEFCDAB89 h2 = 0x98BADCFE h3 = 0x10325476 h4 = 0xC3D2E1F0? Why?
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137 views

SHA-1 colission resistance proof

I'm searching Why the SHA-1 is collision resistance? Anybody could help me with the proof or say me where I can find this proof?
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403 views

How hard/easy will be to break a SHA-1 or SHA-256 hash if the attacker knows part of the original text?

I'm creating an algorithm to hash some text variables (20/30 characters long) to send them across an insecure channel. I'm not dealing with high security data, so no credits card numbers or any other ...
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1answer
290 views

Can I use SHA1 as license key?

I have recently started looking into creating secure, while not validating against an external server, software product keys. The idea I have had is to create a key consisting of two parts firstly a ...
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412 views

probability of N hash digits colliding

What is the probability of the first N hash digits colliding? for example i made a script that appends the first 5 digits of the file's sha1 hash to the name of the file. So will the probability of ...
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562 views

HMAC-SHA1 input size

I know that the HMAC is a message authentication code that uses a cryptographic key in conjunction with a hash function (SHA1 , MD5, etc.). The HMAC output is 160 bits for HMAC-SHA160 and 256 bits for ...
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2k views

Is truncating a SHA512 hash to the first 160 bits as secure as using SHA1?

I am from a web development background (I don't know an awful lot about cryptography or how the algorithms themselves work), so I am asking this question in simple terms. Consider a hash of the word ...
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1k views

How is input message for SHA-2 padded?

I read about how is an input message prepared to be hashed by MD4,MD5 or SHA-1: Step1 Append padding bits The input message is "padded" (extended) so that its length (in bits) equals to 448 ...
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186 views

Difference between actual attacks and theoretical attacks on SHA cryptographic series

Could anyone tell me what the difference is between a THEORETICAL ATTACK (Like the one done on SHA-1) and an actual attack (Like the one done on SHA-0). Is a theoretical attack a proposed method of ...
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355 views

What does “message schedule” mean in SHA-256?

I am trying to understand the sha-256 algorithm from FIPS 180-2. I understood the padding and parsing of the message string. However after that it states (page 15): For $i = 1$ to $N$: { ...
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636 views

Is Wikipedia's table about SHA-2 collisions correct?

I was looking a Wikipedia article on SHA-2, and the "Comparison of SHA functions" table seems to indicate that SHA-2 is less secure than SHA-1. Is this true, or is the table wrong / misleading? ...
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773 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?
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363 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?
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85 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 ...
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2answers
279 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. ...
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994 views

Is it possible to generate an RSA SHA1 signature only from a 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): ...
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39 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 ...
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2answers
787 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 ...
2
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1answer
500 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 ...
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306 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. ...
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5k views

No SHA-1 collision? Yet SHA-1 is broken?

Is there a known pair of distinct bit strings (A,B) such that SHA-1(A) == SHA-1(B)? If the answer is no than how can SHA-1 be considered broken?
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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? ...