client = Aws::CognitoIdentityProvider::Client.new(
  access_key_id: "xxxx",
  secret_access_key: "xxxx",
  region: "us-east-1"
)

# Base64 ( HMAC_SHA256 ( "Client Secret Key", "Username" + "Client Id" ) )
username = "dinesh16@gmail.com"
key = App_client_secret  # (get this from amazon cognito console)
data = username + App_client_id # (get App_client_id from amazon console)

secret_hash = Base64.encode64(OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha256'), key, data)).strip

resp = client.sign_up({
  client_id: "xxx", # required
  secret_hash: secret_hash,
  username: username, # required
  password: "AbCdEpoioQ!", # required
  user_attributes: [
    {
      name: "email", # required
      value: "dinesh16@gmail.com",
    },
  ],
  analytics_metadata: {
    analytics_endpoint_id: "StringType",
  },
  user_context_data: {
    encoded_data: "StringType",
  },
})