encryptiongorsapublic-key-encryptionencryption-asymmetric

How to encrypt large file with RSA?

Code https://play.golang.org/p/CUEqjsJq5c

Error:

panic: crypto/rsa: message too long for RSA public key size

goroutine 1 [running]:
panic(0x4a6d80, 0xc420010420)
    /usr/local/go/src/runtime/panic.go:500 +0x1a1
main.main()
    /tmp/sample.go:28 +0xfa

File size 811 byte (for test encrypt self source file). I want encrypt some bigger files, 1..500 mb. Can I do it with RSA or need use some other methods?

Solution

  • RSA can only encrypt data smaller than (or equal to) the key length.

    The answer is to encrypt the data with a symmetric algorithm such as AES which is designed to encrypt small and large data.

    If an RSA public/private key pair are required encrypt the symmetric (AES) key with RSA. This is referred to as hybrid encryption and in essence is how HTTPS encrypts data.

    But it is may not necessary to RSA encrypt the symmetric key unless a public/private key pair are required. In the general case one just uses symmetric (AES) and that key. What is the use case for a public/private key pair?