md5 | 易学教程

Get MD5 Checksum for Very Large Files

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问题 I've written a script that reads through all files in a directory and returns md5 hash for each file. However, it renders nothing for a rather large file. I assume that the interpreter has some value set for maximum processing time, and since it takes too long to get this value, it just skips along to other files. Is there anyway to get an md5 checksum for large files through PHP? If not, could it be done through a chron job with cpanel? I gave it a shot there but it doesn't seem that my

Can an MD5-hash begin with a zero?

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Can an MD5-hash begin with a zero? What about SHA-1? Yes: $ echo -n "363" | md5sum 00411460f7c92d2124a67ea0f4cb5f85 - $ echo -n "351" | sha1sum 0026476a20bfbd08714155bb66f0b4feb2d25c1c Found by running the following in bash: for i in {1..1000} ; do echo $(echo -n $i | md5sum) $i ; done | sort | head I found a MD5 hash that beginns with a zero byte! 2 character String Unicode #7358 #34823 $returnValue = md5('Ჾ蠇'); result: 00000000 5e0a51c8 313ffb43 8a3a2861 Of course. Or two zeros. Or more. In general, the probability of a "random" input hashing to a result with k leading zero nybbles is about

Is the result of a md5 hash consistant or server dependent?

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问题 I am doing a md5 hash, and just want to make sure the result of: md5.ComputeHash(bytePassword); Is consistent regardless of the server? e.g. windows 2003/2008 and 32/64 bit etc. 回答1: Yes, it's consistent, the md5 algorithm specification defines it regardless of platform. 回答2: MD5 is independent of operating system and architecture. So it is "consistent". However , MD5 takes as input an arbitrary sequence of bits, and outputs a sequence of 128 bits. In many situations, you want strings. For

Hash algorithm with alphanumeric output of 20 characters max

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I need an hash algorithm that outputs an alphanumeric string that is max 20 characters long. For "alphanumeric" I mean [a-zA-Z0-9] . Inputs are UUID s in canonical form (example 550e8400-e29b-41d4-a716-446655440000 ) In alternative is there a way to convert a SHA1 or MD5 hash to a string with these limitations? Thanks. EDIT Doesn't need to be cryptographically secure. Collisions make data inaccurate, but if they happen sporadically I can live with it. EDIT 2 I don't know if truncating MD5 or SHA1 would make collisions happen too often. Now I'm wondering if it's better to truncate to 20 chars a

when I hash a file with Md5 what is hashed?

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问题 is it just the file contents that get hashed? Is there any way to include the file name and or metadata such as creation date into the hashing process? 回答1: In general, all the file hashers encrypts only the binary content of the file. You can prove this with the following process: Apply the md5 algorithm to a file Copy this file into other directory and change its name. Apply the md5 algorithm to the copy. Compare both of the results. They are equal! 回答2: MD5 tools will generally work with

diff files comparing only first n characters of each line

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I have got 2 files. Let us call them md5s1.txt and md5s2.txt. Both contain the output of a find -type f -print0 | xargs -0 md5sum | sort > md5s.txt command in different directories. Many files were renamed, but the content stayed the same. Hence, they should have the same md5sum. I want to generate a diff like diff md5s1.txt md5s2.txt but it should compare only the first 32 characters of each line, i.e. only the md5sum, not the filename. Lines with equal md5sum should be considered equal. The output should be in normal diff format. Easy starter: diff <(cut -d' ' -f1 md5s1.txt) <(cut -d' ' -f1

Decrypt ( with PHP ) a Java encryption ( PBEWithMD5AndDES )

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问题 Someone asked me to decrypt with PHP a string encrypted with the following Java Class. public class CryptoLibrary { private Cipher encryptCipher; private sun.misc.BASE64Encoder encoder = new sun.misc.BASE64Encoder(); public CryptoLibrary() throws SecurityException{ java.security.Security.addProvider(new com.sun.crypto.provider.SunJCE()); char[] pass = "NNSHHETJKKSNKH".toCharArray(); byte[] salt = { (byte) 0xa3, (byte) 0x21, (byte) 0x24, (byte) 0x2c, (byte) 0xf2, (byte) 0xd2, (byte) 0x3e,

Truncating an md5 hash, How do I calculate the odds of a collision occurring?

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I want to truncate an md5 hash to about half size. How much does that increase the odds of collisions? if I'm dealing with around 500 000 generations, should I be worried about a collision? what about 1m generations. The math you're looking for is on Wikipedia's birthday attack page. We consider the following experiment. From a set of H values we choose n values uniformly at random thereby allowing repetitions. Let p(n; H) be the probability that during this experiment at least one value is chosen more than once. This probability can be approximated as With 128 bits the chance of a collision

Will md5(file_contents_as_string) equal md5_file(/path/to/file)?

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If I do: <?php echo md5(file_get_contents("/path/to/file")) ?> ...will this always produce the same hash as: <?php echo md5_file("/path/to/file") ?> Yes they return the same: var_dump(md5(file_get_contents(__FILE__))); var_dump(md5_file(__FILE__)); which returns this in my case: string(32) "4d2aec3ae83694513cb9bde0617deeea" string(32) "4d2aec3ae83694513cb9bde0617deeea" Edit: Take a look at the source code of both functions: https://github.com/php/php-src/blob/master/ext/standard/md5.c (Line 47 & 76). They both use the same functions to generate the hash except that the md5_file() function

is hashing mechanism really secure?

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Well, I have always seen (and following) people saying to use hashing mechanism for storing passwords in database. I am really concerned is it secure? Lets go with example. Let's say I am hacker and I got your database name, id and password. Now I have FULL access to your database. What people say passwords should be hashed because if someone hacks, they are visible to hackers. so If I run query as select id, password FROM userDetails I will get data as below Option 1 : Without hash ++++++++++++++++++++++++++++ + id + password + ++++++++++++++++++++++++++++ + id01 + password01 + + id02 +