card

Documentation

Overview

* Code for generating a printable wallet-sized card containing random password characters.

Index

• Constants
• func CreateRandomSeed() (string, error)
• func DigestSeed(seed string) ([]byte, error)
• type Card
  • func CreateCard(digestedSeed []byte, width, height int) (*Card, error)
  • func (self *Card) Erase()
  • func (self *Card) String() string
• type Coord
  • func MakeCoordinates(key []byte, count, cardSizeX, cardSizeY int, ...) ([]Coord, error)
  • func (self Coord) String() string
• type CoordinateNameFunc

Constants

const SeedLength = 32

The number of characters in a seed (after removing dashes and spaces)

Functions

func CreateRandomSeed

func CreateRandomSeed() (string, error)

*Generate a new seed from a secure-random source (crypto/rand). The seed has slightly more than 128bits of entropy. It is encoded as 32 A-Z characters. The last two characters are a checksum. Having only A-Z characters makes it easier for users to input their seed (especially on a mobile device). The seed is formatted for easy reading as 8 groups of 4, separated by dashes like so:

ATXK-XGFG-TSPF-JSCG-KEMD-YTBJ-ZWEB-LDVW

The A-Z encoding is one-way. To convert the seed to bytes, hash it with sha256 (uppercase, without the dashes).

This operation should only be done on a trusted computer.

func DigestSeed

func DigestSeed(seed string) ([]byte, error)

* Convert the human readable seed, like "ATXK-XGFG-TSPF-JSCG-KEMD-YTBJ-ZWEB-LDVW", to bytes. Returns an error if the seed is malformed or corrupt. The seed is not case sensitive and dashes and spaces are ignored.

Types

type Card

type Card struct {
	// contains filtered or unexported fields
}

func CreateCard

func CreateCard(digestedSeed []byte, width, height int) (*Card, error)

func (*Card) Erase

func (self *Card) Erase()

func (*Card) String

func (self *Card) String() string

Return \n delimited lines

type Coord

type Coord struct {
	//Horizontal coordinate index, starting at 0
	X int
	//Vertical coordinate index, starting at 0
	Y int

	//The human friendly representation (eg "13W").
	HumanX string
	HumanY string
}

*A coordinate on the card

func MakeCoordinates

func MakeCoordinates(key []byte, count, cardSizeX, cardSizeY int,
	xNameFunc, yNameFunc CoordinateNameFunc) ([]Coord, error)

*Given the 32 byte secret key, deterministically generate `count` X,Y coordinates in the range [0,cardSizeX), [0,cardSizeY). The human friendly names for the coordinates are produced by xNameFunc and yNameFunc

func (Coord) String

func (self Coord) String() string

type CoordinateNameFunc

type CoordinateNameFunc func(index int) string