cmix

Documentation

Overview

Any extensions or modifications to the core messaging functionality should be done here, except for conversion of the encrypted message types to the comms messages used for transmitting data.

Any extensions or modifications to the core messaging functionality should be done here, except for conversion of the encrypted message types to the comms messages used for transmitting data.

Package cmix derives new keys within the cyclic group from salts and a symmetric key, locked to a monotonic roundID counter. It also is used for managing keys and salts for communication between clients

Package cmix derives new keys within the cyclic group from salts and a base key. It also is used for managing keys and salts for communication between clients

Package cmix derives new keys within the cyclic group from salts and a base key. It also is used for managing keys and salts for communication between clients

Index

• func ClientEncrypt(grp *cyclic.Group, msg format.Message, salt []byte, ...) format.Message
• func ClientKeyGen(grp *cyclic.Group, salt []byte, roundID id.Round, symmetricKeys []*cyclic.Int) *cyclic.Int
• func GenerateClientGatewayKey(baseKey *cyclic.Int) []byte
• func GenerateKMAC(salt []byte, symmetricKey *cyclic.Int, roundID id.Round, h hash.Hash) []byte
• func GenerateKMACs(salt []byte, symmetricKeys []*cyclic.Int, roundID id.Round, h hash.Hash) [][]byte
• func NewSalt(csprng csprng.Source, size int) []byte
• func NodeKeyGen(grp *cyclic.Group, salt []byte, roundID id.Round, ...)
• func SelectGroupBit(payload, prime []byte, rng csprng.Source) bool
• func SetGroupBits(msg format.Message, grp *cyclic.Group, rng csprng.Source)
• func VerifyKMAC(expectedKmac, salt []byte, symmetricKey *cyclic.Int, roundID id.Round, ...) bool

Functions

func ClientEncrypt

func ClientEncrypt(grp *cyclic.Group, msg format.Message,
	salt []byte, symmetricKeys []*cyclic.Int, roundID id.Round) format.Message

ClientEncrypt encrypts the message for the client by multiplying the inverted encryption key by the message payload

func ClientKeyGen

func ClientKeyGen(grp *cyclic.Group, salt []byte, roundID id.Round,
	symmetricKeys []*cyclic.Int) *cyclic.Int

ClientKeyGen generate encryption key for clients.

func GenerateClientGatewayKey

func GenerateClientGatewayKey(baseKey *cyclic.Int) []byte

GenerateClientGatewayKey hashes the symmetric key between client and the node

func GenerateKMAC

func GenerateKMAC(salt []byte, symmetricKey *cyclic.Int, roundID id.Round,
	h hash.Hash) []byte

GenerateKMAC hashes the salt and base key together using the passed in hashing algorithm to produce a kmac

func GenerateKMACs

func GenerateKMACs(salt []byte, symmetricKeys []*cyclic.Int, roundID id.Round,
	h hash.Hash) [][]byte

GenerateKMACs creates a list of KMACs all with the same salt but different base keys

func NewSalt

func NewSalt(csprng csprng.Source, size int) []byte

NewSalt creates a byte slice of `size` using the provided output from the given cryptographically secure pseudo-random number generator

func NodeKeyGen

func NodeKeyGen(grp *cyclic.Group, salt []byte, roundID id.Round, symmetricKey, output *cyclic.Int)

NodeKeyGen generates encryption key for nodes.

func SelectGroupBit

func SelectGroupBit(payload, prime []byte, rng csprng.Source) bool

selectGroupBit selects what the "group bit" (the highest order bit in the payload) should be it will randomly choose 1 or 0 in the event that choosing 1 will keep the payload in the group, otherwise it will default to 0. true - set the bit to 1 false - set the bit to 0

func SetGroupBits

func SetGroupBits(msg format.Message, grp *cyclic.Group, rng csprng.Source)

SetGroupBits takes a message and a cyclic group and randomly sets the highest order bit in its 2 sub payloads, defaulting to 0 if 1 would put the sub-payload outside of the cyclic group.

WARNING: the behavior above results in 0 vs 1 biasing. in general, groups used have many (100+) leading 1s, which as a result would cause a bias of ~ 1:(1-2^-numLeadingBits). with a high number of leading bits, this is a non issue, but if a prime is chosen with few or no leading bits, this will cease to solve the tagging attack it is meant to fix

Tagging attack: if the dumb solution of leaving the first bits as 0 is chosen, it is possible for an attacker to 75% of the time (when one or both leading bits flip to 1) identity a message they made multiplied garbage into for a tagging attack. This fix makes the leading its random in order to thwart that attack

func VerifyKMAC

func VerifyKMAC(expectedKmac, salt []byte, symmetricKey *cyclic.Int,
	roundID id.Round, h hash.Hash) bool

VerifyKMAC verifies that the generated GenerateKMAC is the same as the passed in GenerateKMAC