如何Decrypt 具有 AES
解密 AES ciphertext using the correct key, IV, and mode, and verify integrity for authenticated modes.
问题
你有 AES-encrypted ciphertext 和键, 和 need 到 recover 原始 plaintext.
前置条件
- Understanding 的 AES 加密
- Knowledge 的模式和 IV used 为加密
步骤
-
1. Gather all parameters
You need the key, the IV (or nonce), the ciphertext, and the mode used during encryption. For GCM, you also need the authentication tag. All of these must match what was used to encrypt.
输入key + IV + ciphertext + mode输出ready to decrypt -
2. Verify the authentication tag (GCM)
If the data was encrypted with GCM, verify the tag before decrypting. If the tag does not match, the ciphertext has been tampered with and must be rejected. Do not attempt to use tampered data.
输入tag mismatch输出reject: data corrupted -
3. Decrypt and interpret the result
Decrypt the ciphertext using the key and IV. If the result is text, decode it with the correct character set. If it is binary, save it as a file. A wrong key produces garbage without error in non-authenticated modes.
输入ciphertext + correct key输出original plaintext
预期结果
原始 plaintext, verified 为完整性如果已认证模式是 used.
常见错误
- Decryption succeeds but output is garbage
- In CBC or CTR mode, a wrong key produces random-looking output without error. Use GCM to detect wrong keys via tag verification.
- Wrong IV produces partially correct output
- The IV affects only the first block in CBC. A wrong IV corrupts the first block but leaves the rest intact. Verify the IV matches.
排障指引
- If only the first block is corrupted, the IV is wrong but the key is correct.
- If all blocks are garbage, the key or mode is wrong.
安全限制
- Never use decrypted data without verifying the authentication tag in GCM mode.
- All decryption happens locally. No data is sent to any server.