✏️ Editing: cdesc-Digest.ri Read Only

U:RDoc::NormalClass[iI"Digest:ETI"OpenSSL::Digest;TI"OpenSSL::Digest::Class;To:RDoc::Markup::Document:@parts[o;;[�:
@fileI"&ext/openssl/lib/openssl/digest.rb;T:0@omit_headings_from_table_of_contents_below0o;;[ o:RDoc::Markup::Paragraph;[	I"FOpenSSL::Digest allows you to compute message digests (sometimes ;TI"Ainterchangeably called "hashes") of arbitrary data that are ;TI"Icryptographically secure, i.e. a Digest implements a secure one-way ;TI"function.;To:RDoc::Markup::BlankLine�o;;[I"DOne-way functions offer some useful properties. E.g. given two ;TI"Edistinct inputs the probability that both yield the same output ;TI"Jis highly unlikely. Combined with the fact that every message digest ;TI"Jalgorithm has a fixed-length output of just a few bytes, digests are ;TI"Joften used to create unique identifiers for arbitrary data. A common ;TI"Jexample is the creation of a unique id for binary documents that are ;TI"stored in a database.;T@o;;[	I"LAnother useful characteristic of one-way functions (and thus the name) ;TI"Fis that given a digest there is no indication about the original ;TI"Mdata that produced it, i.e. the only way to identify the original input ;TI"Fis to "brute-force" through every possible combination of inputs.;T@o;;[I"HThese characteristics make one-way functions also ideal companions ;TI"Gfor public key signature algorithms: instead of signing an entire ;TI"Ldocument, first a hash of the document is produced with a considerably ;TI"Jfaster message digest algorithm and only the few bytes of its output ;TI"Jneed to be signed using the slower public key algorithm. To validate ;TI"Lthe integrity of a signed document, it suffices to re-compute the hash ;TI":and verify that it is equal to that in the signature.;T@o;;[I"MYou can get a list of all digest algorithms supported on your system by ;TI"+running this command in your terminal:;T@o:RDoc::Markup::Verbatim;[I"%openssl list -digest-algorithms
;T:@format0o;;[I"EAmong the OpenSSL 1.1.1 supported message digest algorithms are:;To:RDoc::Markup::List:
@type:BULLET:@items[o:RDoc::Markup::ListItem:@label0;[o;;[I">SHA224, SHA256, SHA384, SHA512, SHA512-224 and SHA512-256;To;;0;[o;;[I".SHA3-224, SHA3-256, SHA3-384 and SHA3-512;To;;0;[o;;[I"BLAKE2s256 and BLAKE2b512;T@o;;[I"AEach of these algorithms can be instantiated using the name:;T@o;
;[I",digest = OpenSSL::Digest.new('SHA256')
;T;0o;;[I"E"Breaking" a message digest algorithm means defying its one-way ;TI"Kfunction characteristics, i.e. producing a collision or finding a way ;TI"Gto get to the original data by means that are more efficient than ;TI"Gbrute-forcing etc. Most of the supported digest algorithms can be ;TI"Iconsidered broken in this sense, even the very popular MD5 and SHA1 ;TI"Jalgorithms. Should security be your highest concern, then you should ;TI"7probably rely on SHA224, SHA256, SHA384 or SHA512.;T@S:RDoc::Markup::Heading:
leveli:	textI"Hashing a file;T@o;
;[I"%data = File.binread('document')
;TI",sha256 = OpenSSL::Digest.new('SHA256')
;TI""digest = sha256.digest(data)
;T;0S;;i;I"+Hashing several pieces of data at once;T@o;
;[
I"#data1 = File.binread('file1')
;TI"#data2 = File.binread('file2')
;TI"#data3 = File.binread('file3')
;TI",sha256 = OpenSSL::Digest.new('SHA256')
;TI"sha256 << data1
;TI"sha256 << data2
;TI"sha256 << data3
;TI"digest = sha256.digest
;T;0S;;i;I"Reuse a Digest instance;T@o;
;[I"#data1 = File.binread('file1')
;TI",sha256 = OpenSSL::Digest.new('SHA256')
;TI"$digest1 = sha256.digest(data1)
;TI"
;TI"#data2 = File.binread('file2')
;TI"sha256.reset
;TI"#digest2 = sha256.digest(data2);T;0;	I"ext/openssl/ossl_digest.c;T;
0;	0;
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0[	I"&ext/openssl/lib/openssl/digest.rb;TI"ext/openssl/ossl.c;TI""lib/rubygems/s3_uri_signer.rb;TI"lib/rubygems/source/git.rb;TI"OpenSSL;TcRDoc::NormalModule

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