Comment en Utiliser RSA Chiffrement

问题

You besoin en chiffrer données avec un public clé donc ce seulement le holder de le privé clé peut déchiffrer it.

Prérequis

• Understanding of public-key cryptography
• Knowledge of key sizes and padding

Étapes

1. 1. Generate or obtain a key pair

   Generate an RSA key pair of at least 2048 bits; 3072 or 4096 bits are recommended for long-term security. The public key can be shared freely; the private key must be kept secret. Alternatively, obtain the recipient's public key.

   entrée

   key size: 4096

   输出

   public key + private key

2. 2. Encrypt with OAEP padding

   Use OAEP (Optimal Asymmetric Encryption Padding) with a hash like SHA-256. Never use PKCS#1 v1.5 padding for encryption, as it is vulnerable to padding oracle attacks. RSA can only encrypt data smaller than the key size minus padding overhead.

   entrée

   small message + public key

   输出

   ciphertext

3. 3. Decrypt with the private key

   The private key holder decrypts the ciphertext using OAEP with the same hash. For large data, encrypt a symmetric key with RSA and encrypt the data with AES (hybrid encryption). This is how TLS and PGP work.

   entrée

   ciphertext + private key

   输出

   original message

Résultat attendu

Données encrypted avec un public clé ce seulement le corresponding privé clé peut déchiffrer.

Erreurs courantes

Message is too long for RSA

RSA can only encrypt data up to key_size - padding_overhead bytes. Use hybrid encryption: encrypt an AES key with RSA and the data with AES.

Using PKCS#1 v1.5 padding

PKCS#1 v1.5 is vulnerable to Bleichenbacher's padding oracle attack. Always use OAEP.

Dépannage指引

• If decryption fails, verify the padding scheme and hash match on both sides.
• For large files, use hybrid encryption rather than chunking with RSA directly.

Limites de sécurité

• RSA key sizes below 2048 bits are considered insecure. Use 3072+ bits for new applications.
• All operations are local. Private keys never leave your machine.