The paper proposes a novel approach to constructing CCA-secure public-key encryption schemes from any CPA-secure identity-based encryption (IBE) scheme. The construction requires the IBE scheme to satisfy only a "weak" notion of security, which is known to be achievable without random oracles. This provides a new method for building CCA-secure encryption schemes in the standard model, avoiding the use of non-interactive proofs of "well-formedness" that have been central to previous constructions. The technique is also extended to secure binary tree encryption (BTE) schemes against adaptive chosen-ciphertext attacks, leading to more efficient CCA-secure hierarchical identity-based and forward-secure encryption schemes in the standard model. The authors also discuss the implications of their work for "black-box" separations and related cryptographic constructions.The paper proposes a novel approach to constructing CCA-secure public-key encryption schemes from any CPA-secure identity-based encryption (IBE) scheme. The construction requires the IBE scheme to satisfy only a "weak" notion of security, which is known to be achievable without random oracles. This provides a new method for building CCA-secure encryption schemes in the standard model, avoiding the use of non-interactive proofs of "well-formedness" that have been central to previous constructions. The technique is also extended to secure binary tree encryption (BTE) schemes against adaptive chosen-ciphertext attacks, leading to more efficient CCA-secure hierarchical identity-based and forward-secure encryption schemes in the standard model. The authors also discuss the implications of their work for "black-box" separations and related cryptographic constructions.