Replace blake2b by sha512 (as it is not yet available on alpine

token-validator/challenge.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"crypto/hmac"
+	"crypto/sha512"
 	"encoding/hex"
 	"encoding/json"
 	"errors"
@@ -13,7 +14,6 @@ import (
 	"time"
 
 	"github.com/julienschmidt/httprouter"
-	"golang.org/x/crypto/blake2b"
 )
 
 const IPgwDMZ = "172.23.200.1"
@@ -129,7 +129,7 @@ func challengeDisk(s *Student, t *givenToken, chid int) error {
 		return err
 	}
 
-	expectedToken := blake2b.Sum512([]byte(pkey[n1:n2]))
+	expectedToken := sha512.Sum512([]byte(pkey[n1:n2]))
 
 	if ! hmac.Equal(expectedToken[:], sum) {
 		return errors.New("This is not the expected token.")