Class: EllipticCurve::PublicKey

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

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(point, curve) ⇒ PublicKey

Returns a new instance of PublicKey.



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# File 'lib/publickey.rb', line 11

def initialize(point, curve)
    @point = point
    @curve = curve
end

Instance Attribute Details

#curve ⇒ Object

Returns the value of attribute curve.



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# File 'lib/publickey.rb', line 9

def curve
  @curve
end

#point ⇒ Object

Returns the value of attribute point.



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# File 'lib/publickey.rb', line 9

def point
  @point
end

Class Method Details

.fromCompressed(string, curve = Curve::SECP256K1) ⇒ Object 



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# File 'lib/publickey.rb', line 98

def self.fromCompressed(string, curve=Curve::SECP256K1)
    parityTag, xHex = string[0..1], string[2..-1]
    if not [EvenTag, OddTag].include? parityTag
        raise Exception.new("Compressed string should start with 02 or 03")
    end
    x = Utils::Binary.intFromHex(xHex)
    y = curve.y(x=x, isEven=parityTag == EvenTag)
    return PublicKey.new(point=Point.new(x, y), curve=curve)
end

.fromDer(string) ⇒ Object 



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# File 'lib/publickey.rb', line 56

def self.fromDer(string)
    hexadecimal = Utils::Binary.hexFromByteString(string)
    curveData, pointString = Utils::Der.parse(hexadecimal)[0]
    publicKeyOid, curveOid = curveData
    if publicKeyOid != EcdsaPublicKeyOid
        raise Exception.new("The Public Key Object Identifier (OID) should be #{EcdsaPublicKeyOid}, but #{publicKeyOid} was found instead")
    end
    curve = Curve.getbyOid(curveOid)
    return self.fromString(pointString, curve)
end

.fromPem(string) ⇒ Object 



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# File 'lib/publickey.rb', line 51

def self.fromPem(string)
    publicKeyPem = Utils::Pem.getContent(string, PemTemplate)
    return self.fromDer(Utils::Binary.byteStringFromBase64(publicKeyPem))
end

.fromString(string, curve = Curve::SECP256K1, validatePoint = true) ⇒ Object 



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# File 'lib/publickey.rb', line 67

def self.fromString(string, curve=Curve::SECP256K1, validatePoint=true)
    baseLength = 2 * curve.length
    if string.length > 2 * baseLength and string[0..3] == "0004"
        string = string[4..-1]
    end

    xs = string[0..baseLength - 1]
    ys = string[baseLength..-1]

    p = Point.new(
        Utils::Binary.intFromHex(xs), 
        Utils::Binary.intFromHex(ys)
    )

    publicKey = PublicKey.new(p, curve)
    if not validatePoint
        return publicKey
    end
    if p.isAtInfinity()
        raise Exception.new("Public key point at infinity")
    end
    if not curve.contains(p)
        raise Exception.new("Point (#{p.x}, #{p.y}) is not valid for curve #{curve.name}")
    end
    if not Math.multiply(p, curve.n, curve.n, curve.a, curve.p).isAtInfinity()
        raise Exception.new("Point (#{p.x}, #{p.y}) * #{curve.name}.n is not at infinity")
    end
    
    return publicKey
end

Instance Method Details

#toCompressed ⇒ Object 



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# File 'lib/publickey.rb', line 28

def toCompressed
    baseLength = 2 * @curve.length
    parityTag = @point.y % 2 == 0 ? EvenTag : OddTag
    xHex = Utils::Binary.hexFromInt(@point.x).rjust(baseLength, "0")
    return parityTag + xHex
end

#toDer ⇒ Object 



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# File 'lib/publickey.rb', line 35

def toDer
    @hexadecimal = Utils::Der.encodeConstructed(
        Utils::Der.encodeConstructed(
            Utils::Der.encodePrimitive(Utils::Der::DerFieldType.object, EcdsaPublicKeyOid),
            Utils::Der.encodePrimitive(Utils::Der::DerFieldType.object, @curve.oid)
        ),
        Utils::Der.encodePrimitive(Utils::Der::DerFieldType.bitString, self.toString(true))       
    )
    return Utils::Binary.byteStringFromHex(@hexadecimal)
end

#toPem ⇒ Object 



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# File 'lib/publickey.rb', line 46

def toPem
    der = self.toDer()
    return Utils::Pem.create(Utils::Binary.base64FromByteString(der), PemTemplate)
end

#toString(encoded = false) ⇒ Object 



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# File 'lib/publickey.rb', line 16

def toString encoded=false
    baseLength = 2 * @curve.length

    xHex = Utils::Binary.hexFromInt(@point.x).rjust(baseLength, "0")
    yHex = Utils::Binary.hexFromInt(@point.y).rjust(baseLength, "0")
    string = xHex + yHex
    if encoded 
        return "0004" + string
    end
    return string
end