class Digest::SHA2

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..."

Public Class Methods

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.

# File ext/digest/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

Public Instance Methods

digest_obj << string → digest_obj

Alias for: update

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

# File ext/digest/sha2/lib/sha2.rb, line 112
def block_length
  @sha2.block_length
end

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.

# File ext/digest/sha2/lib/sha2.rb, line 130
def digest_length
  @sha2.digest_length
end

reset → digest_obj

Reset the digest to the initial state and return self.

# File ext/digest/sha2/lib/sha2.rb, line 79
def reset
  @sha2.reset
  self
end

update(string) → digest_obj

Update the digest using a given string and return self.

# File ext/digest/sha2/lib/sha2.rb, line 89
def update(str)
  @sha2.update(str)
  self
end

Also aliased as: <<