Asymmetric Encryption in Rust

Compute
1

Ever wonder how to decrypt data that get passed between clients and your origin servers? With Fastly Compute it is a piece of cake. The following fiddle is a quick example for how to do asymmetric decryption.

We have a few interesting characters in this code:

  1. DEMO_RSA_KEY: An insecure RSA private key that’s only in the script for demonstration.
  2. main function: Extracts a special header called X-Base64-Cipher.
  3. decrypt_base64_encoded_value: This function does the following:
  • Base64‑decodes the ciphertext from a string into raw bytes.
  • Loads the RSA private key.
  • Decrypts the ciphertext using PKCS#1.
  • Returns the original human‑readable plaintext.

With RSA, you typically encrypt using a public key and decrypt using the private key. In this code, we assume someone has already used the public key to encrypt a message (turning hello_world_from_alice into cipher bytes). This code then decrypts the ciphertext, turning gibberish back into the original message.

Try it out yourself. Use the following openssl commands to generate a private key and public key which may be used for encryption.

# Make the private key
openssl genrsa -out private_key.pem 2048

# Make the public key
openssl rsa -in private_key.pem -pubout -out public_key.pem

# Encrypt the string to use in the header
echo -n "hello_world_from_alice" | \
openssl pkeyutl -encrypt -pubin -inkey public_key.pem -pkeyopt rsa_padding_mode:pkcs1 | \
base64
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