Class: Bitcoin::SLIP39::Share

Inherits:
Object
  • Object
show all
Defined in:
lib/bitcoin/slip39/share.rb

Overview

Share of Shamir’s Secret Sharing Scheme

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#checksum ⇒ Object

30 bits, Integer



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# File 'lib/bitcoin/slip39/share.rb', line 15

def checksum
  @checksum
end

#group_count ⇒ Object

4 bits, Integer



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# File 'lib/bitcoin/slip39/share.rb', line 11

def group_count
  @group_count
end

#group_index ⇒ Object

4 bits, Integer



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# File 'lib/bitcoin/slip39/share.rb', line 9

def group_index
  @group_index
end

#group_threshold ⇒ Object

4 bits, Integer



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# File 'lib/bitcoin/slip39/share.rb', line 10

def group_threshold
  @group_threshold
end

#id ⇒ Object

15 bits, Integer



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# File 'lib/bitcoin/slip39/share.rb', line 7

def id
  @id
end

#iteration_exp ⇒ Object

5 bits, Integer



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# File 'lib/bitcoin/slip39/share.rb', line 8

def iteration_exp
  @iteration_exp
end

#member_index ⇒ Object

4 bits, Integer



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# File 'lib/bitcoin/slip39/share.rb', line 12

def member_index
  @member_index
end

#member_threshold ⇒ Object

4 bits, Integer



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# File 'lib/bitcoin/slip39/share.rb', line 13

def member_threshold
  @member_threshold
end

#value ⇒ Object

8n bits, hex string.



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# File 'lib/bitcoin/slip39/share.rb', line 14

def value
  @value
end

Class Method Details

.from_words(words) ⇒ Bitcoin::SLIP39::Share

Recover Share from the mnemonic words

Parameters:

Returns:

Raises:

  • (ArgumentError) 


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# File 'lib/bitcoin/slip39/share.rb', line 20

def self.from_words(words)
  raise ArgumentError, 'Mnemonics should be an array of strings' unless words.is_a?(Array)
  indices = words.map do |word|
    index = Bitcoin::SLIP39::WORDS.index(word.downcase)
    raise IndexError, 'word not found in words list.' unless index
    index
  end

  raise ArgumentError, 'Invalid mnemonic length.' if indices.size < MIN_MNEMONIC_LENGTH_WORDS
  raise ArgumentError, 'Invalid mnemonic checksum.' unless verify_rs1024_checksum(indices)

  padding_length = (RADIX_BITS * (indices.size - METADATA_LENGTH_WORDS)) % 16
  raise ArgumentError, 'Invalid mnemonic length.' if padding_length > 8
  data = indices.map{|i|i.to_s(2).rjust(10, '0')}.join

  s = self.new
  s.id = data[0...ID_LENGTH_BITS].to_i(2)
  s.iteration_exp = data[ID_LENGTH_BITS...(ID_LENGTH_BITS + ITERATION_EXP_LENGTH_BITS)].to_i(2)
  s.group_index = data[20...24].to_i(2)
  s.group_threshold = data[24...28].to_i(2) + 1
  s.group_count = data[28...32].to_i(2) + 1
  raise ArgumentError, "Invalid mnemonic. Group threshold(#{s.group_threshold}) cannot be greater than group count(#{s.group_count})." if s.group_threshold > s.group_count
  s.member_index = data[32...36].to_i(2)
  s.member_threshold = data[36...40].to_i(2) + 1
  value_length = data.length - 70
  start_index = 40 + padding_length
  end_index = start_index + value_length - padding_length
  padding_value = data[40...(40 + padding_length)]
  raise ArgumentError, "Invalid mnemonic. padding must only zero." unless padding_value.to_i(2) == 0
  s.value = data[start_index...end_index].to_i(2).to_even_length_hex
  s.checksum = data[(40 + value_length)..-1].to_i(2)
  s
end

.rs1024_polymod(values) ⇒ Object 



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# File 'lib/bitcoin/slip39/share.rb', line 68

def self.rs1024_polymod(values)
  gen = [0xe0e040, 0x1c1c080, 0x3838100, 0x7070200, 0xe0e0009, 0x1c0c2412, 0x38086c24, 0x3090fc48, 0x21b1f890, 0x3f3f120]
  chk = 1
  values.each do |v|
    b = (chk >> 20)
    chk = (chk & 0xfffff) << 10 ^ v
    10.times do |i|
      chk ^= (((b >> i) & 1 == 1) ? gen[i] : 0)
    end
  end
  chk
end

Instance Method Details

#calculate_checksum ⇒ Integer

Calculate checksum using current fields

Returns:



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# File 'lib/bitcoin/slip39/share.rb', line 63

def calculate_checksum
  indices = build_word_indices(false)
  create_rs1024_checksum(indices).map{|i|i.to_bits(10)}.join.to_i(2)
end

#to_words ⇒ Array[String]

Generate mnemonic words

Returns:



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# File 'lib/bitcoin/slip39/share.rb', line 56

def to_words
  indices = build_word_indices
  indices.map{|index| Bitcoin::SLIP39::WORDS[index]}
end