Update:
"Canonical signatures" are not secure, strongly unforgeable signatures are really needed here http://crypto.stanford.edu/~dabo/papers/strongsigs.pdf. But other approaches gives the same benefits, It's better to choose approach 2 or 3.
Transaction malleability in cryptocurrencies
Update:
"Canonical signatures" are not secure, strongly unforgeable signatures are really needed here http://crypto.stanford.edu/~dabo/papers/strongsigs.pdf. But other approaches gives the same benefits, It's better to choose approach 2 or 3.