Class: Digest::SHA2

Inherits:
Class
  • Object
show all
Defined in:
sha2/lib/sha2.rb

Overview

A meta digest provider class for SHA256, SHA384 and SHA512.

FIPS 180-2 describes SHA2 family of digest algorithms. It defines three algorithms:

  • one which works on chunks of 512 bits and returns a 256-bit digest (SHA256),

  • one which works on chunks of 1024 bits and returns a 384-bit digest (SHA384),

  • and one which works on chunks of 1024 bits and returns a 512-bit digest (SHA512).

Examples

require 'digest'

# Compute a complete digest
Digest::SHA2.hexdigest 'abc'          # => "ba7816bf8..."
Digest::SHA2.new(256).hexdigest 'abc' # => "ba7816bf8..."
Digest::SHA256.hexdigest 'abc'        # => "ba7816bf8..."

Digest::SHA2.new(384).hexdigest 'abc' # => "cb00753f4..."
Digest::SHA384.hexdigest 'abc'        # => "cb00753f4..."

Digest::SHA2.new(512).hexdigest 'abc' # => "ddaf35a19..."
Digest::SHA512.hexdigest 'abc'        # => "ddaf35a19..."

# Compute digest by chunks
sha2 = Digest::SHA2.new               # =>#<Digest::SHA2:256>
sha2.update "ab"
sha2 << "c"                           # alias for #update
sha2.hexdigest                        # => "ba7816bf8..."

# Use the same object to compute another digest
sha2.reset
sha2 << "message"
sha2.hexdigest                        # => "ab530a13e..."

Instance Method Summary collapse

Methods inherited from Class

base64digest, bubblebabble, digest, file, hexdigest

Methods included from Instance

#==, #base64digest, #base64digest!, #bubblebabble, #digest, #digest!, #file, #hexdigest, #hexdigest!, #length, #new, #size, #to_s

Constructor Details

#initialize(bitlen = 256) ⇒ SHA2

call-seq:

Digest::SHA2.new(bitlen = 256) -> digest_obj

Create a new SHA2 hash object with a given bit length.

Valid bit lengths are 256, 384 and 512.



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# File 'sha2/lib/sha2.rb', line 61

def initialize(bitlen = 256)
  case bitlen
  when 256
    @sha2 = Digest::SHA256.new
  when 384
    @sha2 = Digest::SHA384.new
  when 512
    @sha2 = Digest::SHA512.new
  else
    raise ArgumentError, "unsupported bit length: %s" % bitlen.inspect
  end
  @bitlen = bitlen
end

Instance Method Details

#block_length ⇒ Object

call-seq:

digest_obj.block_length -> Integer

Return the block length of the digest in bytes.

Digest::SHA256.new.block_length * 8
# => 512
Digest::SHA384.new.block_length * 8
# => 1024
Digest::SHA512.new.block_length * 8
# => 1024



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# File 'sha2/lib/sha2.rb', line 112

def block_length
  @sha2.block_length
end

#digest_length ⇒ Object

call-seq:

digest_obj.digest_length -> Integer

Return the length of the hash value (the digest) in bytes.

Digest::SHA256.new.digest_length * 8
# => 256
Digest::SHA384.new.digest_length * 8
# => 384
Digest::SHA512.new.digest_length * 8
# => 512

For example, digests produced by Digest::SHA256 will always be 32 bytes (256 bits) in size.



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# File 'sha2/lib/sha2.rb', line 130

def digest_length
  @sha2.digest_length
end

#initialize_copy(other) ⇒ Object

:nodoc:



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# File 'sha2/lib/sha2.rb', line 134

def initialize_copy(other) # :nodoc:
  @sha2 = other.instance_eval { @sha2.clone }
end

#inspect ⇒ Object

:nodoc:



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# File 'sha2/lib/sha2.rb', line 138

def inspect # :nodoc:
  "#<%s:%d %s>" % [self.class.name, @bitlen, hexdigest]
end

#reset ⇒ Object

call-seq:

digest_obj.reset -> digest_obj

Reset the digest to the initial state and return self.



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# File 'sha2/lib/sha2.rb', line 79

def reset
  @sha2.reset
  self
end

#update(str) ⇒ Object Also known as: <<

call-seq:

digest_obj.update(string) -> digest_obj
digest_obj << string -> digest_obj

Update the digest using a given string and return self.



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# File 'sha2/lib/sha2.rb', line 89

def update(str)
  @sha2.update(str)
  self
end