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

Source

# 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

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

Valid bit lengths are 256, 384 and 512.

Public Instance Methods

digest_obj << string → digest_obj

Alias for: update

block_length → Integer

Source

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

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

digest_length → Integer

Source

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

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.

reset → digest_obj

Source

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

Reset the digest to the initial state and return self.

update(string) → digest_obj

Source

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

Update the digest using a given string and return self.

Also aliased as: <<

Private Instance Methods

instance_eval { finish } → digest_obj

Source

static VALUE
rb_digest_instance_finish(VALUE self)
{
    rb_digest_instance_method_unimpl(self, "finish");

    UNREACHABLE;
}

Finishes the digest and returns the resulting hash value.

This method is overridden by each implementation subclass and often made private, because some of those subclasses may leave internal data uninitialized. Do not call this method from outside. Use digest!() instead, which ensures that internal data be reset for security reasons.