This paper presents a new method for constructing chosen-ciphertext (CCA) secure public-key encryption schemes from any chosen-plaintext (CPA) secure identity-based encryption (IBE) schemes. The proposed construction requires only a "weak" notion of security for the underlying IBE scheme, which is known to be achievable without random oracles. This approach is significantly different from previous methods, which often rely on non-interactive proofs of "well-formedness." The new method avoids these proofs and results in more efficient and practical CCA-secure encryption schemes. The technique is extended to provide a simple and efficient method for securing any binary tree encryption (BTE) scheme against adaptive chosen-ciphertext attacks. This leads to more efficient CCA-secure hierarchical identity-based and forward-secure encryption schemes in the standard model. The paper also discusses implications for "black-box" separations, showing that the construction of a CCA-secure encryption scheme from a weak IBE scheme is black-box in nature. It also highlights the efficiency of the proposed method, noting that it can be applied to recent IBE schemes to produce practical CCA-secure encryption schemes. The paper further extends the technique to construct CCA-secure BTE schemes from any BTE scheme secure against selective-node, chosen-plaintext attacks. This results in more efficient constructions of CCA-secure hierarchical identity-based and forward-secure encryption schemes. The paper concludes with a discussion of related work, including the use of tag-based non-malleability (tnm) in constructing CCA-secure cryptosystems. It also notes that the proposed method can be used to construct CCA-secure encryption schemes from any weak IBE scheme with minimal overhead.This paper presents a new method for constructing chosen-ciphertext (CCA) secure public-key encryption schemes from any chosen-plaintext (CPA) secure identity-based encryption (IBE) schemes. The proposed construction requires only a "weak" notion of security for the underlying IBE scheme, which is known to be achievable without random oracles. This approach is significantly different from previous methods, which often rely on non-interactive proofs of "well-formedness." The new method avoids these proofs and results in more efficient and practical CCA-secure encryption schemes. The technique is extended to provide a simple and efficient method for securing any binary tree encryption (BTE) scheme against adaptive chosen-ciphertext attacks. This leads to more efficient CCA-secure hierarchical identity-based and forward-secure encryption schemes in the standard model. The paper also discusses implications for "black-box" separations, showing that the construction of a CCA-secure encryption scheme from a weak IBE scheme is black-box in nature. It also highlights the efficiency of the proposed method, noting that it can be applied to recent IBE schemes to produce practical CCA-secure encryption schemes. The paper further extends the technique to construct CCA-secure BTE schemes from any BTE scheme secure against selective-node, chosen-plaintext attacks. This results in more efficient constructions of CCA-secure hierarchical identity-based and forward-secure encryption schemes. The paper concludes with a discussion of related work, including the use of tag-based non-malleability (tnm) in constructing CCA-secure cryptosystems. It also notes that the proposed method can be used to construct CCA-secure encryption schemes from any weak IBE scheme with minimal overhead.