Winston Smith

Winston Smith

Ruby programmer. Watching by the Big Brother.

RSA Signature and Verifying in Ruby

3 minute read

RSA (Rivest–Shamir–Adleman) is one of the first public-key cryptosystems and is widely used for secure data transmission

Generate a key pair, the server will use the public key, the client will use the private key.

  1. Client will generate a signature using the private key{\displaystyle h={\text{hash))(m);}
  2. Server will verify the signature using the public key{\displaystyle (h^{e})^{d}=h^{ed}=h^{de}=(h^{d})^{e}\equiv h{\pmod {n))}
require 'openssl'

# Generate the key pairs, and give client the private key
pkey = OpenSSL::PKey::RSA.new(2048)
private_key = pkey.to_pem # or to_der, depends on client

# Client
data = "Sign me!"
pkey = OpenSSL::PKey::RSA.new(private_key)
signature = pkey.sign("SHA256", data)

# Server
pub_key = pkey.public_key
pub_key.verify("SHA256", signature, data) # true

RSA (cryptosystem)

OpenSSL::PKey::RSA

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