Abstract:Honest-sender commitments were introduced to construct non-interactive and non-malleable commitments. In this paper, two honest-sender commitments are given: The first one is honest-sender statistically binding and the second one is perfectly hiding. Neither of them is a commitment scheme, which implies that honest-sender commitment is a weaker cryptographic primitive than commitment scheme. In addition, this paper defines honest-receiver commitment and gives two constructions: The first one has the statistically binding property and the second has the honest-receiver perfectly hiding property. Both of them are not commitment scheme, which implies that honest-receiver commitment is a weaker cryptographic primitive than commitment scheme.