Module: PQCrypto::Seal::Padding

Defined in:
lib/pq_crypto/seal/padding.rb

Class Method Summary collapse

Class Method Details

.fixed_or_buckets(base_length, policy) ⇒ Object 



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# File 'lib/pq_crypto/seal/padding.rb', line 32

def fixed_or_buckets(base_length, policy)
  if policy.key?(:to)
    target = Integer(policy.fetch(:to))
    raise InvalidConfigurationError, "padding target is smaller than envelope" if target < base_length
    target
  elsif policy.key?(:buckets)
    bucket = Array(policy.fetch(:buckets)).map { |n| Integer(n) }.sort.find { |n| n >= base_length }
    raise InvalidConfigurationError, "no padding bucket can hold envelope" unless bucket
    bucket
  else
    raise InvalidConfigurationError, "padding hash must contain :to or :buckets"
  end
end

.padme_target(length) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/pq_crypto/seal/padding.rb', line 8

def padme_target(length)
  n = Integer(length)
  raise ArgumentError, "length must be non-negative" if n.negative?
  return n if n <= 1

  exponent = n.bit_length - 1
  significant = exponent.bit_length
  low_bits = exponent - significant
  return n if low_bits <= 0

  mask = (1 << low_bits) - 1
  (n + mask) & ~mask
end

.target(base_length, policy) ⇒ Object 



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# File 'lib/pq_crypto/seal/padding.rb', line 22

def target(base_length, policy)
  case policy
  when nil, :none then base_length
  when :padme then padme_target(base_length)
  when Hash then fixed_or_buckets(base_length, policy)
  else
    raise InvalidConfigurationError, "unsupported padding policy: #{policy.inspect}"
  end
end