Use all available threads for argon2

wrappers/keyDeriv.go

@@ -1,6 +1,8 @@
 package wrappers
 
 import (
+	"runtime"
+
 	"golang.org/x/crypto/argon2"
 	"golang.org/x/crypto/chacha20poly1305"
 )
@@ -9,13 +11,14 @@ const (
 	// parameters for Argon2
 	argonTime   = 1
 	argonMemory = 64 * 1024
-	argonThreads = 4
 	argonKeyLen = chacha20poly1305.KeySize
 
 	// general constants
 	saltSize = 16
 )
 
+var argonThreads = uint8(runtime.NumCPU())
+
 // DeriveKey derives an encryption key from a passphrase using Argon2.
 func deriveKey(passphrase []byte, salt []byte) []byte {
 	return argon2.IDKey(passphrase, salt, argonTime, argonMemory, argonThreads, argonKeyLen)