diff --git a/crypto/gopenpgp.go b/crypto/gopenpgp.go
index 0e599e4..2884b31 100644
--- a/crypto/gopenpgp.go
+++ b/crypto/gopenpgp.go
@@ -8,13 +8,13 @@ import "sync"
 type GopenPGP struct {
 	latestServerTime int64
 	generationOffset int64
-	lock             *sync.Mutex
+	lock             *sync.RWMutex
 }
 
 var pgp = GopenPGP{
 	latestServerTime: 0,
 	generationOffset: 0,
-	lock: &sync.Mutex{},
+	lock: &sync.RWMutex{},
 }
 
 // clone returns a clone of the byte slice. Internal function used to make sure
diff --git a/crypto/time.go b/crypto/time.go
index a20529b..b208d87 100644
--- a/crypto/time.go
+++ b/crypto/time.go
@@ -36,8 +36,8 @@ func GetTime() time.Time {
 
 // getNow returns the latest server time.
 func getNow() time.Time {
-	pgp.lock.Lock()
-	defer pgp.lock.Unlock()
+	pgp.lock.RLock()
+	defer pgp.lock.RUnlock()
 
 	if pgp.latestServerTime == 0 {
 		return time.Now()
@@ -53,8 +53,8 @@ func getTimeGenerator() func() time.Time {
 
 // getNowKeyGenerationOffset returns the current time with the key generation offset.
 func getNowKeyGenerationOffset() time.Time {
-	pgp.lock.Lock()
-	defer pgp.lock.Unlock()
+	pgp.lock.RLock()
+	defer pgp.lock.RUnlock()
 
 	if pgp.latestServerTime == 0 {
 		return time.Unix(time.Now().Unix()+pgp.generationOffset, 0)