Class: EllipticCurve::Utils::RandomInteger

Inherits:
Object
  • Object
show all
Defined in:
lib/utils/integer.rb

Class Method Summary collapse

Class Method Details

._digestNameFromLength(hLen) ⇒ Object 



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# File 'lib/utils/integer.rb', line 73

def self._digestNameFromLength(hLen)
    case hLen
    when 32
        "SHA256"
    when 48
        "SHA384"
    when 64
        "SHA512"
    when 20
        "SHA1"
    else
        "SHA256"
    end
end

.between(min, max) ⇒ Object

Return integer x in the range: min <= x <= max

Parameters (required): :param min: minimum value of the integer :param max: maximum value of the integer :return: A random number between min and max



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# File 'lib/utils/integer.rb', line 13

def self.between(min, max)
    if (max - min) < 0 then
        raise Exception.new("max must be greater than min")
    end
    if (max - min) > 0 then
        return SecureRandom.random_number((max + 1) - min) + min
    end
    return min
end

.rfc6979(hashBytes, secret, curve, hashfunc) ⇒ Object 



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# File 'lib/utils/integer.rb', line 23

def self.rfc6979(hashBytes, secret, curve, hashfunc)
    # Generate nonce values per hedged RFC 6979: deterministic k derivation
    # with fresh random entropy mixed into K-init (RFC 6979 ยง3.6). Same message
    # and key yield different signatures, while preserving RFC 6979's protection
    # against RNG failures.
    orderBitLen = curve.nBitLength
    orderByteLen = (orderBitLen + 7) / 8

    secretHex = Binary.hexFromInt(secret).rjust(orderByteLen * 2, "0")
    secretBytes = Binary.byteStringFromHex(secretHex)

    hashReduced = Binary.numberFromByteString(hashBytes, orderBitLen) % curve.n
    hashHex = Binary.hexFromInt(hashReduced).rjust(orderByteLen * 2, "0")
    hashOctets = Binary.byteStringFromHex(hashHex)

    extraEntropyHex = Binary.hexFromInt(between(0, (1 << (orderByteLen * 8)) - 1)).rjust(orderByteLen * 2, "0")
    extraEntropy = Binary.byteStringFromHex(extraEntropyHex)

    hLen = hashfunc.call("").bytesize
    digestName = _digestNameFromLength(hLen)
    v = "\x01".b * hLen
    k = "\x00".b * hLen

    k = OpenSSL::HMAC.digest(digestName, k, v + "\x00".b + secretBytes + hashOctets + extraEntropy)
    v = OpenSSL::HMAC.digest(digestName, k, v)
    k = OpenSSL::HMAC.digest(digestName, k, v + "\x01".b + secretBytes + hashOctets + extraEntropy)
    v = OpenSSL::HMAC.digest(digestName, k, v)

    Enumerator.new do |yielder|
        loop do
            t = "".b
            while t.bytesize * 8 < orderBitLen
                v = OpenSSL::HMAC.digest(digestName, k, v)
                t += v
            end

            kCandidate = Binary.numberFromByteString(t, orderBitLen)

            if kCandidate >= 1 && kCandidate <= curve.n - 1
                yielder.yield kCandidate
            end

            k = OpenSSL::HMAC.digest(digestName, k, v + "\x00".b)
            v = OpenSSL::HMAC.digest(digestName, k, v)
        end
    end
end