passwords

Documentation

Index

• Variables
• func ComparePasswordAndHash(password, hash string) (match bool, err error)
• func CreateHash(password string, params *Params) (hash string, err error)
• func GenerateRandom(length uint32) string
• func MustCreateHash(password string, params *Params) string
• type Params

Variables

var (
	// ErrInvalidHash in returned by ComparePasswordAndHash if the provided
	// hash isn't in the expected format.
	ErrInvalidHash = errors.New("passwords: hash is not in the correct format")

	// ErrIncompatibleVersion in returned by ComparePasswordAndHash if the
	// provided hash was created using a different version of Argon2.
	ErrIncompatibleVersion = errors.New("passwords: incompatible version of argon2")
)

var DefaultParams = &Params{
	Memory:      64 * 1024,
	Iterations:  3,
	Parallelism: 2,
	SaltLength:  16,
	KeyLength:   40,
}

DefaultParams provides some sane default parameters for hashing passwords. You are encouraged to change the Memory, Iterations and Parallelism parameters to values appropraite for the environment that your code will be running in.

Functions

func ComparePasswordAndHash

func ComparePasswordAndHash(password, hash string) (match bool, err error)

ComparePasswordAndHash performs a constant-time comparison between a plain-text password and Argon2id hash, using the parameters and salt contained in the hash. It returns true if they match, otherwise it returns false.

func CreateHash

func CreateHash(password string, params *Params) (hash string, err error)

CreateHash returns a Argon2id hash of a plain-text password using the provided algorithm parameters. The returned hash follows the format used by the Argon2 reference C implementation and contains the base64-encoded Argon2id d derived key prefixed by the salt and parameters. It looks like this:

$argon2id$v=19$m=65536,t=3,p=2$c29tZXNhbHQ$RdescudvJCsgt3ub+b+dWRWJTmaaJObG

func GenerateRandom

func GenerateRandom(length uint32) string

GenerateRandom creates a random human-readable string by Base58 Encoding random bytes

func MustCreateHash

func MustCreateHash(password string, params *Params) string

MustCreateHash is the same as CreateHash, but panics on error

Types

type Params

type Params struct {
	// The amount of memory used by the algorithm (in kibibytes).
	Memory uint32

	// The number of iterations over the memory.
	Iterations uint32

	// The number of threads (or lanes) used by the algorithm.
	Parallelism uint8

	// Length of the random salt. 16 bytes is recommended for password hashing.
	SaltLength uint32

	// Length of the generated key. 16 bytes or more is recommended.
	KeyLength uint32
}

Params describes the input parameters used by the Argon2id algorithm. The Memory and Iterations parameters control the computational cost of hashing the password. The higher these figures are, the greater the cost of generating the hash and the longer the runtime. It also follows that the greater the cost will be for any attacker trying to guess the password. If the code is running on a machine with multiple cores, then you can decrease the runtime without reducing the cost by increasing the Parallelism parameter. This controls the number of threads that the work is spread across. Important note: Changing the value of the Parallelism parameter changes the hash output.

For guidance and an outline process for choosing appropriate parameters see https://tools.ietf.org/html/draft-irtf-cfrg-argon2-04#section-4