title: Verify signed data vault offline
body: <p>I'm sending to a client a public_key and a payload plus a signature.</p>
  
  <p>I'm trying to verify the signature on the client using the public_key and payload but I can't find a way to get the data verified. Every time I receive false as a response regardless of what I'm doing.</p>
  
  <p>I'm using vault to sign the payload</p>
  
  <pre><code>  def sign(box_identifier, data) do
         Vaultex.Client.write("transit/sign/#{box_identifier}",
                       %{ 
                          input: data,
                          hash_algorithm: "sha2-256"
                        },
                       @authentication_strategy,
                       {@token})
    end
  
    Vault.Transit.sign("coucou", Base.encode64("test"))
  
     _____________________________________________________________
     digest = OpenSSL::Digest::SHA256.new
     key = OpenSSL::PKey::RSA.new File.read 'key.pem'       
  
     key.public_key.verify digest, signature, "test"
  
  
  -----BEGIN PUBLIC KEY-----
  MIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEAzj0qLxEc0Qu9g9nxdMRe
  jBaUD0+GuQITiAPEDOrjScJTznJrR9hXqO14BqepuEmcz4irv4hEkBEBfqZ1XnP9
  2fc9zG4A20lepqDRwPhkEdI4D71KRPSxv/a+O2HrAhTYH17NbsYDtpkFCdepC6FC
  01aso679d3kAZiZ+GD2OLDWifreBVPE2aXacJYXZZ4kTkchsevY3PnAcOG4LmM6b
  kUoF1qfP6tJ/VItJXyqSC2PI9Io28zFhwOf6cPLEQCBCTNCNwHunqHW8olcE/Xfn
  b2toym0/UvW3kH/P4h+TE1ZoCV5FWwcx9hcAy1TC0zm4D5Xwt0/4Pgj1GiXFGOY4
  WKGyuDK8gs7QsSDqu+B5p0xiDg7226bpplVxR/P87CohYTtYZj/lO03G2ZEj3pCr
  /juxThdzTgO5xUcPV5GFbPjlK1TIIb5XVZZzW6+sviB6cYZ5T/Xp9dtbR8G9Zt9n
  gLlaKU7U/DDQxRv2uiCZy5U/DUpfxY56r4Y73Ir2YgmZY1PKLC2a5/w3wScVZILN
  fnxnVYOzSPPaKxAJWbZsZjxXJS0veE8RgGFHgWfe8+qPCEnx81Jf2NzupQHO1KIk
  UnlYGcPESk/90psDNsmISSdtF2D6j4k28k0ncViTu2eMKBX81W8TgTeHtQa3zR0S
  upN2o25b3Wi2oQU14kTdOCcCAwEAAQ==
  -----END PUBLIC KEY-----
  </code></pre>
  
  <p>Am I even capable of validating the signature offline when its signed by vault ?</p>