The Lizard Method of Point Reversal

A common operation on elliptic curves is to hash data onto a point onto the curve. But can we reverse the point back to the hashed data? For this, we can use the Lizard method within a Ristretto group constructed from Edwards25519. It was first defined by Abraham Westerbaan [1]:

Overall, if we do not want to reverse the point back to data, we should use the Derive() method:

Ristretto prime-order group built from Edwards25519

If we need to reverse the point back to data, we can use the SetLizard() method:

m:="Hello"
 
var p ristretto.Point

 h := sha256.Sum256([]byte(m))

 var ret [16]byte
 copy(ret[:], h[:])

 
 p.SetLizard(&ret) 

In this case, we create a SHA256 hash, and then copy 16 bytes into the curve point (p). To reverse, we can then apply [here]:

m:="Hello" 
var p ristretto.Point
 var outBuf [16]byte

 h := sha256.Sum256([]byte(m))

 var ret [16]byte
 copy(ret[:], h[:])

 
 p.SetLizard(&ret)…