diff --git a/README.md b/README.md
index c3c8d5d5..f36ebd29 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,7 @@ Current features:
 - [x] Revoking Certificates
 - [ ] Initiating account recovery
 - Identifier validation challenges
-  - [x] SimpleHTTP Challenge
+  - [x] SimpleHTTP Challenge (Scheduled for removal on Nov 19th)
   - [x] HTTP (http-01)
   - [ ] TLS with Server Name Indication (tls-sni-01)
   - [ ] Proof of Possession of a Prior Key (proofOfPossession-01)
diff --git a/acme/crypto.go b/acme/crypto.go
index 608ec7d4..73bd9c99 100644
--- a/acme/crypto.go
+++ b/acme/crypto.go
@@ -9,6 +9,7 @@ import (
 	"crypto/rsa"
 	"crypto/x509"
 	"crypto/x509/pkix"
+	"encoding/base64"
 	"encoding/binary"
 	"encoding/pem"
 	"errors"
@@ -16,6 +17,7 @@ import (
 	"io/ioutil"
 	"math/big"
 	"net/http"
+	"strings"
 	"time"
 
 	"golang.org/x/crypto/ocsp"
@@ -115,6 +117,27 @@ func GetOCSPForCert(bundle []byte) ([]byte, int, error) {
 	return ocspResBytes, ocspRes.Status, nil
 }
 
+func getKeyAuthorization(token string, key interface{}) (string, error) {
+	// Generate the Key Authorization for the challenge
+	jwk := keyAsJWK(key)
+	if jwk == nil {
+		return "", errors.New("Could not generate JWK from key.")
+	}
+	thumbBytes, err := jwk.Thumbprint(crypto.SHA256)
+	if err != nil {
+		return "", err
+	}
+
+	// unpad the base64URL
+	keyThumb := base64.URLEncoding.EncodeToString(thumbBytes)
+	index := strings.Index(keyThumb, "=")
+	if index != -1 {
+		keyThumb = keyThumb[:index]
+	}
+
+	return token + "." + keyThumb, nil
+}
+
 // Derive the shared secret according to acme spec 5.6
 func performECDH(priv *ecdsa.PrivateKey, pub *ecdsa.PublicKey, outLen int, label string) []byte {
 	// Derive Z from the private and public keys according to SEC 1 Ver. 2.0 - 3.3.1
diff --git a/acme/http_challenge.go b/acme/http_challenge.go
index f0a2d3cc..66ade473 100644
--- a/acme/http_challenge.go
+++ b/acme/http_challenge.go
@@ -1,8 +1,6 @@
 package acme
 
 import (
-	"crypto"
-	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -27,19 +25,11 @@ func (s *httpChallenge) Solve(chlng challenge, domain string) error {
 	s.end = make(chan error)
 
 	// Generate the Key Authorization for the challenge
-	key := keyAsJWK(&s.jws.privKey.PublicKey)
-	thumbBytes, err := key.Thumbprint(crypto.SHA256)
+	keyAuth, err := getKeyAuthorization(chlng.Token, &s.jws.privKey.PublicKey)
 	if err != nil {
 		return err
 	}
 
-	keyThumb := base64.URLEncoding.EncodeToString(thumbBytes)
-	index := strings.Index(keyThumb, "=")
-	if index != -1 {
-		keyThumb = keyThumb[:index]
-	}
-	keyAuth := chlng.Token + "." + keyThumb
-
 	go s.startHTTPServer(domain, chlng.Token, keyAuth)
 	var listener net.Listener
 	select {