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Class: OpenSSL::HMAC

Relationships & Source Files
Inherits: Object
Defined in: ext/openssl/ossl_hmac.c,
ext/openssl/ossl_hmac.c

Overview

HMAC allows computing Hash-based Message Authentication Code (HMAC). It is a type of message authentication code (MAC) involving a hash function in combination with a key. HMAC can be used to verify the integrity of a message as well as the authenticity.

HMAC has a similar interface to Digest.

HMAC-SHA256 using one-shot interface

key = "key"
data = "message-to-be-authenticated"
mac = OpenSSL::HMAC.hexdigest("SHA256", key, data)
#=> "cddb0db23f469c8bf072b21fd837149bd6ace9ab771cceef14c9e517cc93282e"

HMAC-SHA256 using incremental interface

data1 = File.read("file1")
data2 = File.read("file2")
key = "key"
digest = OpenSSL::Digest::SHA256.new
hmac = OpenSSL::HMAC.new(key, digest)
hmac << data1
hmac << data2
mac = hmac.digest

Class Method Summary

Instance Method Summary

Constructor Details

.new(key, digest) ⇒ HMAC

Returns an instance of HMAC set with the key and digest algorithm to be used. The instance represents the initial state of the message authentication code before any data has been processed. To process data with it, use the instance method #update with your data as an argument.

Example

key = 'key'
digest = OpenSSL::Digest.new('sha1')
instance = OpenSSL::HMAC.new(key, digest)
#=> f42bb0eeb018ebbd4597ae7213711ec60760843f
instance.class
#=> OpenSSL::HMAC

A note about comparisons

Two instances won't be equal when they're compared, even if they have the same value. Use #to_s or #hexdigest to return the authentication code that the instance represents. For example:

other_instance = OpenSSL::HMAC.new('key', OpenSSL::Digest.new('sha1'))
#=> f42bb0eeb018ebbd4597ae7213711ec60760843f
instance
#=> f42bb0eeb018ebbd4597ae7213711ec60760843f
instance == other_instance
#=> false
instance.to_s == other_instance.to_s
#=> true

Class Method Details

.digest(digest, key, data) ⇒ String

Returns the authentication code as a binary string. The digest parameter must be an instance of Digest.

Example

key = 'key'
data = 'The quick brown fox jumps over the lazy dog'
digest = OpenSSL::Digest.new('sha1')

hmac = OpenSSL::HMAC.digest(digest, key, data)
#=> "\xDE|\x9B\x85\xB8\xB7\x8A\xA6\xBC\x8Az6\xF7\n\x90p\x1C\x9D\xB4\xD9"

.to_s(digest, key, data) ⇒ String .hexdigest(digest, key, data) ⇒ String

Alias for .to_s.

.to_s(digest, key, data) ⇒ String .inspect(digest, key, data) ⇒ String

Alias for .to_s.

.to_s(digest, key, data) ⇒ String Also known as: .hexdigest, .inspect

Returns the authentication code as a hex-encoded string. The .digest parameter must be an instance of Digest.

Example

key = 'key'
data = 'The quick brown fox jumps over the lazy dog'
digest = OpenSSL::Digest.new('sha1')

hmac = OpenSSL::HMAC.hexdigest(digest, key, data)
#=> "de7c9b85b8b78aa6bc8a7a36f70a90701c9db4d9"

Instance Method Details

#<<(string) ⇒ self Also known as: #update

Returns self updated with the message to be authenticated. Can be called repeatedly with chunks of the message.

Example

first_chunk = 'The quick brown fox jumps '
second_chunk = 'over the lazy dog'

instance.update(first_chunk)
#=> 5b9a8038a65d571076d97fe783989e52278a492a
instance.update(second_chunk)
#=> de7c9b85b8b78aa6bc8a7a36f70a90701c9db4d9

#digest ⇒ String

Returns the authentication code an instance represents as a binary string.

Example

instance = OpenSSL::HMAC.new('key', OpenSSL::Digest.new('sha1'))
#=> f42bb0eeb018ebbd4597ae7213711ec60760843f
instance.digest
#=> "\xF4+\xB0\xEE\xB0\x18\xEB\xBDE\x97\xAEr\x13q\x1E\xC6\a`\x84?"

#hexdigest ⇒ String

Returns the authentication code an instance represents as a hex-encoded string.

#reset ⇒ self

Returns self as it was when it was first initialized, with all processed data cleared from it.

Example

data = "The quick brown fox jumps over the lazy dog"
instance = OpenSSL::HMAC.new('key', OpenSSL::Digest.new('sha1'))
#=> f42bb0eeb018ebbd4597ae7213711ec60760843f

instance.update(data)
#=> de7c9b85b8b78aa6bc8a7a36f70a90701c9db4d9
instance.reset
#=> f42bb0eeb018ebbd4597ae7213711ec60760843f

#<<(string) ⇒ self #update(string) ⇒ self

Alias for #<<.