Online electronic wallet with decentralized credential keepers is an architecture allowing users to leave most of the content of his electronic wallet at the security of his residential electronic keeper, while traveling with his mobile phone. This paper proposed a new security scheme for mobile payment using such architecture. The approach differs from the previous work in that it uses identity-based encryption for securing payment between the payer and payee, which takes full advantage of public-key cryptography while simplifies the authenticity requirements of the public keys.