diff --git a/docker/bckp/kv_to_s3.go b/docker/bckp/kv_to_s3.go
index 76dc0d7..4cc2133 100644
--- a/docker/bckp/kv_to_s3.go
+++ b/docker/bckp/kv_to_s3.go
@@ -1,21 +1,42 @@
 package main
 import (
   "github.com/hashicorp/consul/api"
-  /*"crypto/aes"*/
+  "errors"
   "log"
+  "fmt"
+  "os"
+  "encoding/base64"
   /*"github.com/aws/aws-sdk-go/service/s3"*/
 )
 
+const consul_addr string = "KV2S3_CONSUL_ADDR"
+const enc_key string = "KV2S3_ENC_KEY"
+
+const key_exp_bits int = 256
+const key_exp_bytes int = key_exp_bits / 8
+
 func errIsPanic(err error, format string, a ...interface{}) {
   if err != nil {
     log.Panicf(format, a...)
   }
 }
 
+func absentIsErr(present bool) error {
+  if !present {
+    return errors.New("Environement variable is not set.")
+  }
+  return nil
+}
+
 func main() {
   log.Println("starting consul kv backup...")
+
+  //--- Ask Consul to Snapshot our KV
+  var present bool
   conf := api.DefaultConfig()
-  //@FIXME add later support for a different URL
+  conf.Address, present = os.LookupEnv(consul_addr)
+  err := absentIsErr(present)
+  errIsPanic(err, "%v env required. %v", consul_addr, err)
   //@FIXME add later support for HTTPS
 
   options := api.QueryOptions {
@@ -26,9 +47,36 @@ func main() {
   consul, err := api.NewClient(conf)
   errIsPanic(err, "Unable to build a new client. %v", err)
 
-  _, _, err = consul.Snapshot().Save(&options)
+  reader, _, err := consul.Snapshot().Save(&options)
   errIsPanic(err, "Snapshot failed. %v", err)
 
+  //--- Get encryption key and check it
+  b64_key, present := os.LookupEnv(enc_key)
+  err = absentIsErr(present)
+  errIsPanic(err, "%v env required. %v", enc_key, err)
+  raw_key, err := base64.StdEncoding.DecodeString(b64_key)
+  errIsPanic(err, "Unable to decode base64 key. %v", err)
+
+  err = nil
+  key_size_bytes := len(raw_key)
+  key_size_bits := key_size_bytes
+
+  if key_size_bytes != key_exp_bytes {
+    msg := fmt.Sprintf(
+      "Key size is %d bits (%d bytes) instead of %d bits (%d bytes).",
+      key_size_bits,
+      key_size_bytes,
+      key_exp_bits,
+      key_exp_bytes)
+
+    err = errors.New(msg)
+  }
+  errIsPanic(err, "We deliberately support only 256 bits (32 bytes) keys. %v", err)
+
+  //--- Encryption
+  // Not a simple thing to do it in a streaming manner
+  // To understand why age by Filippo Valsorda seems to be a good fit:
+  // https://neilmadden.blog/2019/12/30/a-few-comments-on-age/
 
 
 }