RSA加密-公钥加密

Question

I would like to use RSA encryption on a large file (>25 MB). Is it possible or are there limitations using a Public Key/Private Key for a large app? I am exposing a public key to clients and not allowing anyone but the recipient to view the contents with the private key. So the business case makes sense although it will be slower than symmetrical encryption.

Thanks,

Answer 1

RSA cannot encrypt a payload larger than its key size (minus some overhead for padding). To bypass this limitation you'll need to generate a symmetric key, use that to encrypt the larger file, then encrypt the symmetric key itself with RSA (with OAEP or PKCS1v1.5 padding).

Cryptographic Message Syntax (CMS) and PKCS7 (CMS's predecessor) support this use case already so there's no need to invent your own protocol.