Use multiple KDFs (add Scrypt for AES256)

wrappers/keyDeriv.go

@@ -4,21 +4,33 @@ import (
 	"runtime"
 
 	"golang.org/x/crypto/argon2"
+	"golang.org/x/crypto/scrypt"
 )
 
 const (
 	// parameters for Argon2
 	argonTime   = 8          // set to pass 1-second test in dev environment
 	argonMemory = 384 * 1024 // 384 MB
-	argonKeyLen = 32         // 256 bits, key length for both ChaCha20 and AES256
+
+	// parameters for Scrypt
+	scryptN = 262144
+	scryptR = 8 // block size, recommended to be 8
+	scryptP = 1 // parallelization factor, recommended to be 1
 
 	// general constants
-	saltSize = 16
+	keyLen   = 32 // 256 bits, key length for both algorithms
+	saltSize = 16 // 128 bits, recommended salt size for both algorithms
 )
 
-var argonThreads = uint8(runtime.NumCPU())
+var threads = 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)
+// DeriveKeyArgon2 derives an encryption key from a passphrase using Argon2.
+func deriveKeyArgon2(passphrase []byte, salt []byte) []byte {
+	return argon2.IDKey(passphrase, salt, argonTime, argonMemory, threads, keyLen)
+}
+
+// DeriveKeyScrypt derives an encryption key from a passphrase using Scrypt.
+func deriveKeyScrypt(passphrase []byte, salt []byte) []byte {
+	key, _ := scrypt.Key(passphrase, salt, scryptN, scryptR, scryptP, keyLen)
+	return key
 }