Cómo a Usar RSA Cifrado

问题

You necesitar a cifrar datos con un público clave así que ese solo el holder de el privado clave puede descifrar it.

Requisitos previos

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

Pasos

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.

   entrada

   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.

   entrada

   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.

   entrada

   ciphertext + private key

   输出

   original message

Resultado esperado

Datos encrypted con un público clave ese solo el corresponding privado clave puede descifrar.

Errores comunes

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.

Solución de problemas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.

Límites de seguridad

• 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.