In Eurocrypt 2005,Waters' identity-based encryption scheme suffers from a drawback that the scheme only guarantees chosen plaintext security,which hampers its applications in higher security level environments.A chosen ciphertext secure identity-based encryption scheme was proposed to remedy this drawback.The proposed encryption scheme was regarded as the extended version of Waters' scheme with only one additional element in the ciphertext,and guaranteed chosen ciphertext security.The extended scheme's indistinguishability against adaptive chosen ciphertext attacks was proven in the standard model and rested on the hardness of the decisional bilinear Diffie-Hellman intractability assumption.