Class: SecretSharing::Shamir::Container

Inherits:
Object
  • Object
show all
Includes:
SecretSharing::Shamir
Defined in:
lib/secretsharing/shamir/container.rb

Overview

The SecretSharing::Shamir::Container class can be used to share random secrets between n people, so that k < n people can recover the secret, but k-1 people learn nothing (in an information-theoretical sense) about the secret.

For a theoretical background, see:

http://www.cs.tau.ac.il/~bchor/Shamir.html
http://en.wikipedia.org/wiki/Secret_sharing#Shamir.27s_scheme

Constant Summary collapse

MIN_SHARES = 
2
MAX_SHARES = 
512

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from SecretSharing::Shamir

#evaluate_polynomial_at, #get_random_number, #lagrange, #usafe_decode64, #usafe_encode64

Constructor Details

#initialize(n, k = n) ⇒ Container

To create a new SecretSharing::Shamir::Container object, you can pass either just n, or n and k where:

n = The total number of shares that will be created.
k = The threshold number of the total shares needed to
    recreate the original secret. (Default = n)

For example:

# 3(k) out of 5(n) shares needed to recover secret
s = SecretSharing::Shamir::Container.new(5, 3)

# 3(k) out of 3(n) shares needed to recover secret
s = SecretSharing::Shamir::Container.new(3)



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# File 'lib/secretsharing/shamir/container.rb', line 50

def initialize(n, k = n)
  @n               = n.to_i
  @k               = k.to_i

  fail ArgumentError, 'n must be an Integer' unless @n.is_a?(Integer)
  fail ArgumentError, 'k must be an Integer' unless @k.is_a?(Integer)

  fail ArgumentError, 'k must be <= n'              unless @k <= @n
  fail ArgumentError, 'k must be >= #{MIN_SHARES}'  unless @k >= MIN_SHARES
  fail ArgumentError, 'n must be <= #{MAX_SHARES}'  unless @n <= MAX_SHARES

  @secret          = nil
  @shares          = []
end

Instance Attribute Details

#k ⇒ Object (readonly)

Returns the value of attribute k.



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# File 'lib/secretsharing/shamir/container.rb', line 30

def k
  @k
end

#n ⇒ Object (readonly)

Returns the value of attribute n.



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# File 'lib/secretsharing/shamir/container.rb', line 30

def n
  @n
end

#secret ⇒ Object

Returns the value of attribute secret.



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# File 'lib/secretsharing/shamir/container.rb', line 30

def secret
  @secret
end

#shares ⇒ Object (readonly)

Returns the value of attribute shares.



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# File 'lib/secretsharing/shamir/container.rb', line 30

def shares
  @shares
end

Instance Method Details

#<<(share) ⇒ Object

Add a secret share to the object. Accepts a SecretSharing::Shamir::Share instance. Returns secret as a SecretSharing::Shamir::Secret if enough valid shares have been added to recover the secret, and false otherwise. The secret can also be recovered later with SecretSharing::Shamir::Container#secret if enough valid shares were previously provided.



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# File 'lib/secretsharing/shamir/container.rb', line 83

def <<(share)
  # You can't add more shares than were originally generated with value of @n
  fail ArgumentError, 'You have added more shares than allowed by the value of @n' if @shares.size >= @n

  share = SecretSharing::Shamir::Share.new(:share => share) unless share.is_a?(SecretSharing::Shamir::Share)
  @shares << share unless @shares.include?(share)
  @secret = Share.recover_secret(@shares)
end

#secret? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/secretsharing/shamir/container.rb', line 65

def secret?
  @secret.is_a?(SecretSharing::Shamir::Secret)
end