Decryption
Decryption uses the required key to reverse encryption and recover plaintext from ciphertext.
Definition
Decryption is the authorized process that transforms ciphertext back into plaintext with the appropriate algorithm and key. In symmetric cryptography it uses the shared secret key; in asymmetric encryption it normally uses the recipient’s private key.
How decryption works
The decryptor may need the ciphertext, key, nonce or initialization vector, authentication tag, and algorithm parameters. Decoding hexadecimal or Base64 only restores the stored bytes and is not decryption. Authenticated schemes verify the tag before returning plaintext.
Failures and safe handling
A wrong key may produce an error or meaningless bytes; unauthenticated designs cannot always detect the mistake. Applications should reject altered ciphertext, avoid exposing detailed failure information, and protect recovered plaintext in memory, logs, and temporary storage.
Proper modern encryption is intended to make that computationally infeasible. Weak ciphers, small key spaces, implementation flaws, or stolen keys can make recovery possible.
No. Decoding reverses a public representation such as Base64. Decryption reverses a key-controlled security transformation.
Authenticated encryption rejects the data because verification fails. Older or unauthenticated schemes may instead return meaningless output without reliably signaling the error.