crypt(p1) public

Applies a one-way cryptographic hash to str by invoking the standard library function crypt(3) with the given salt string. While the format and the result are system and implementation dependent, using a salt matching the regular expression A{2} should be valid and safe on any platform, in which only the first two characters are significant.

This method is for use in system specific scripts, so if you want a cross-platform hash function consider using Digest or OpenSSL instead.

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May 4, 2009
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Via Kenneth Kalmer:

From the man page: If salt is a character string starting with the characters “$id$” followed by a string terminated by “$”: $id$salt$encrypted then instead of using the DES machine, id identifies the encryption method used and this then determines how the rest of the password string is interpreted.

irb session



March 3, 2011
1 thank

String#crypt uses your platform's native implementation

Which cipher types (specified through the salt argument) are available will depend on what your platform natively supports. It should be noted that OSX up to at last 10.6 only provides the regular DES cipher. On most Linux platforms, however, you should have access to the following:

ID  | Method
1   | MD5
2a  | Blowfish (not in mainline glibc; added in some
    | Linux distributions)
5   | SHA-256 (since glibc 2.7)
6   | SHA-512 (since glibc 2.7)

So on OSX, you might have:

ruby-1.9.2-p180 :001 > "password".crypt("$6$somesalt")
 => "$6FMi11BJFsAc" 

But on Linux, you’ll get:

irb(main):001:0> "password".crypt("$6$somesalt")
=> "$6$somesalt$A7P/0Yfu8RprY88D5T1n.xKT749BOn/IXBvmR1gXZzU7imsoTfZhCQ1916CB7WNX9eOOeSmBmmMrl5fQn9LAP1"

For more information on what your platform supports, see `man crypt`

February 11, 2010 - (v1_8_6_287 - v1_8_7_72)
0 thanks

Clarification of argument

The description should read:

The argument is the salt string, which must be at least two characters long, each character drawn from [a-zA-Z0-9./].

December 7, 2012
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Beware: default system crypt functionality silently ignores characters beyond the 8th

On some systems:

"1".crypt('aa')                     => "aacFCuAIHhrCM"
"12".crypt('aa')                    => "aa8dJzr7DFMPA"
"123".crypt('aa')                   => "aamrgyQfDFSHw"
"1234".crypt('aa')                  => "aatxRPdZ/m52."
"12345".crypt('aa')                 => "aajt.4s3e3SZA"
"123456".crypt('aa')                => "aaAN1ZUwjW7to"
"1234567".crypt('aa')               => "aaOK9MRbwVNmQ"
"12345678".crypt('aa')              => "aaNN3X.PL2piw"
"123456789".crypt('aa')             => "aaNN3X.PL2piw"
"1234567890".crypt('aa')            => "aaNN3X.PL2piw"
"1234567890abcdefghij".crypt('aa')  => "aaNN3X.PL2piw"