class Bitcoin::SLIP39::Share
Share
of Shamir's Secret Sharing Scheme
Attributes
checksum[RW]
group_count[RW]
group_index[RW]
group_threshold[RW]
id[RW]
iteration_exp[RW]
member_index[RW]
member_threshold[RW]
value[RW]
Public Class Methods
from_words(words)
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Recover Share
from the mnemonic words @param [Array{String}] words the mnemonic words @return [Bitcoin::SLIP39::Share] a share
# 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)
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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
Private Class Methods
verify_rs1024_checksum(data)
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Verify RS1024 checksum @param [Array data the array of mnemonic word index @return [Boolean] verify result
# File lib/bitcoin/slip39/share.rb, line 105 def self.verify_rs1024_checksum(data) rs1024_polymod(CUSTOMIZATION_STRING + data) == 1 end
Public Instance Methods
calculate_checksum()
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Calculate checksum using current fields @return [Integer] checksum
# 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()
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Generate mnemonic words @return [Array] array of mnemonic word.
# File lib/bitcoin/slip39/share.rb, line 56 def to_words indices = build_word_indices indices.map{|index| Bitcoin::SLIP39::WORDS[index]} end
Private Instance Methods
build_word_indices(include_checksum = true)
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Create word indices from this share. @param [Boolean] include_checksum whether include checksum when creating indices. @param [Array] the array of index
# File lib/bitcoin/slip39/share.rb, line 86 def build_word_indices(include_checksum = true) s = id.to_bits(ID_LENGTH_BITS) s << iteration_exp.to_bits(ITERATION_EXP_LENGTH_BITS) s << group_index.to_bits(4) s << (group_threshold - 1).to_bits(4) s << (group_count - 1).to_bits(4) raise StandardError, "Group threshold(#{group_threshold}) cannot be greater than group count(#{group_count})." if group_threshold > group_count s << member_index.to_bits(4) s << (member_threshold - 1).to_bits(4) value_length = value.to_i(16).bit_length padding_length = RADIX_BITS - (value_length % RADIX_BITS) s << value.to_i(16).to_bits(value_length + padding_length) s << checksum.to_bits(30) if include_checksum s.chars.each_slice(10).map{|index| index.join.to_i(2)} end
create_rs1024_checksum(data)
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Create RS1024 checksum @param [Array data the array of mnemonic word index without checksum @return [Array] the array of checksum integer
# File lib/bitcoin/slip39/share.rb, line 112 def create_rs1024_checksum(data) values = CUSTOMIZATION_STRING + data + Array.new(CHECKSUM_LENGTH_WORDS, 0) polymod = Bitcoin::SLIP39::Share.rs1024_polymod(values) ^ 1 CHECKSUM_LENGTH_WORDS.times.to_a.reverse.map {|i|(polymod >> (10 * i)) & 1023 } end