Ruby OpenSSL::PKey::RSA generate RSA Public Key from Modulus and Exponent

ruby_generate_pubkey.rb

# [A] OpenSSL::PKey::RSA has undocumented `e=' and `n=' methods
exponent = "10001"
modulus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

rsa   = OpenSSL::PKey::RSA.new
e     = exponent.to_i(16)
n     = modulus.to_i(16)
rsa.e = OpenSSL::BN.new(e)
rsa.n = OpenSSL::BN.new(n)

rsa.public_encrypt("something")


# [B] simplified with `.tap'
rsa = OpenSSL::PKey::RSA.new.tap do |rsa|
  rsa.e = OpenSSL::BN.new(exponent)
  rsa.n = OpenSSL::BN.new(modulus)
end

rsa.public_encrypt("something")

If you're here trying to figure out how to do this on Ubuntu 22 / OpenSSL 3: https://gist.github.com/WilliamNHarvey/0e37f84a86e66f9acb7ac8c68b0f996b