diff --git a/directory.go b/directory.go
index 8ff2659..83fb477 100644
--- a/directory.go
+++ b/directory.go
@@ -60,7 +60,7 @@ func gcf_list_dir(sessionID int, dirName string) (*C.char, *C.int, C.int) {
 	var cachedIV []byte
 	if !OpenedVolumes[sessionID].plainTextNames {
 		// Read the DirIV from disk
-		cachedIV, err = nametransform.ReadDirIVAt(fd)
+		cachedIV, err = volume.nameTransform.ReadDirIVAt(fd)
 		if err != nil {
 			return nil, nil, 0
 		}
diff --git a/helpers.go b/helpers.go
index 51b3437..bf60ec7 100644
--- a/helpers.go
+++ b/helpers.go
@@ -50,7 +50,7 @@ func (volume *Volume) openBackingDir(relPath string) (dirfd int, cName string, e
 	// Walk the directory tree
 	parts := strings.Split(relPath, "/")
 	for i, name := range parts {
-		iv, err := nametransform.ReadDirIVAt(dirfd)
+		iv, err := volume.nameTransform.ReadDirIVAt(dirfd)
 		if err != nil {
 			syscall.Close(dirfd)
 			return -1, "", err
@@ -112,7 +112,7 @@ func (volume *Volume) prepareAtSyscall(path string) (dirfd int, cName string, er
 	// Cache store
 	if !volume.plainTextNames {
 		// TODO: openBackingDir already calls ReadDirIVAt(). Avoid duplicate work?
-		iv, err := nametransform.ReadDirIVAt(dirfd)
+		iv, err := volume.nameTransform.ReadDirIVAt(dirfd)
 		if err != nil {
 			syscall.Close(dirfd)
 			return -1, "", err
diff --git a/internal/configfile/config_file.go b/internal/configfile/config_file.go
index d50b71b..ffc41de 100644
--- a/internal/configfile/config_file.go
+++ b/internal/configfile/config_file.go
@@ -5,9 +5,7 @@ package configfile
 import (
 	"encoding/json"
 	"fmt"
-	"io"
 	"io/ioutil"
-	"log"
 	"syscall"
 
 	"os"
@@ -60,64 +58,66 @@ type ConfFile struct {
 	filename string
 }
 
-// randBytesDevRandom gets "n" random bytes from /dev/random or panics
-func randBytesDevRandom(n int) []byte {
-	f, err := os.Open("/dev/random")
-	if err != nil {
-		log.Panic("Failed to open /dev/random: " + err.Error())
-	}
-	defer f.Close()
-	b := make([]byte, n)
-	_, err = io.ReadFull(f, b)
-	if err != nil {
-		log.Panic("Failed to read random bytes: " + err.Error())
-	}
-	return b
+// CreateArgs exists because the argument list to Create became too long.
+type CreateArgs struct {
+	Filename           string
+	Password           []byte
+	PlaintextNames     bool
+	LogN               int
+	Creator            string
+	AESSIV             bool
+	DeterministicNames bool
+	XChaCha20Poly1305  bool
 }
 
 // Create - create a new config with a random key encrypted with
-// "password" and write it to "filename".
-// Uses scrypt with cost parameter logN.
-func Create(filename string, password []byte, plaintextNames bool,
-	logN int, creator string, aessiv bool, devrandom bool, fido2CredentialID []byte, fido2HmacSalt []byte) error {
-	var cf ConfFile
-	cf.filename = filename
-	cf.Creator = creator
-	cf.Version = contentenc.CurrentVersion
-
-	// Set feature flags
-	cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagGCMIV128])
-	cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagHKDF])
-	if plaintextNames {
-		cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagPlaintextNames])
+// "Password" and write it to "Filename".
+// Uses scrypt with cost parameter "LogN".
+func Create(args *CreateArgs) error {
+	cf := ConfFile{
+		filename: args.Filename,
+		Creator:  args.Creator,
+		Version:  contentenc.CurrentVersion,
+	}
+	// Feature flags
+	cf.setFeatureFlag(FlagHKDF)
+	if args.XChaCha20Poly1305 {
+		cf.setFeatureFlag(FlagXChaCha20Poly1305)
 	} else {
-		cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagDirIV])
-		cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagEMENames])
-		cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagLongNames])
-		cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagRaw64])
+		// 128-bit IVs are mandatory for AES-GCM (default is 96!) and AES-SIV,
+		// XChaCha20Poly1305 uses even an even longer IV of 192 bits.
+		cf.setFeatureFlag(FlagGCMIV128)
 	}
-	if aessiv {
-		cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagAESSIV])
-	}
-	if len(fido2CredentialID) > 0 {
-		cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[FlagFIDO2])
-		cf.FIDO2 = &FIDO2Params{
-			CredentialID: fido2CredentialID,
-			HMACSalt:     fido2HmacSalt,
+	if args.PlaintextNames {
+		cf.setFeatureFlag(FlagPlaintextNames)
+	} else {
+		if !args.DeterministicNames {
+			cf.setFeatureFlag(FlagDirIV)
 		}
+		cf.setFeatureFlag(FlagEMENames)
+		cf.setFeatureFlag(FlagLongNames)
+		cf.setFeatureFlag(FlagRaw64)
+	}
+	if args.AESSIV {
+		cf.setFeatureFlag(FlagAESSIV)
+	}
+	// Catch bugs and invalid cli flag combinations early
+	cf.ScryptObject = NewScryptKDF(args.LogN)
+	if err := cf.Validate(); err != nil {
+		return err
+	}
+	// Catch bugs and invalid cli flag combinations early
+	cf.ScryptObject = NewScryptKDF(args.LogN)
+	if err := cf.Validate(); err != nil {
+		return err
 	}
 	{
 		// Generate new random master key
-		var key []byte
-		if devrandom {
-			key = randBytesDevRandom(cryptocore.KeyLen)
-		} else {
-			key = cryptocore.RandBytes(cryptocore.KeyLen)
-		}
+		key := cryptocore.RandBytes(cryptocore.KeyLen)
 		// Encrypt it using the password
 		// This sets ScryptObject and EncryptedKey
 		// Note: this looks at the FeatureFlags, so call it AFTER setting them.
-		cf.EncryptKey(key, password, logN, false)
+		cf.EncryptKey(key, args.Password, args.LogN, false)
 		for i := range key {
 			key[i] = 0
 		}
@@ -175,39 +175,22 @@ func Load(filename string) (*ConfFile, error) {
 		return nil, err
 	}
 
-	if cf.Version != contentenc.CurrentVersion {
-		return nil, fmt.Errorf("Unsupported on-disk format %d", cf.Version)
-	}
-
-	// Check that all set feature flags are known
-	for _, flag := range cf.FeatureFlags {
-		if !cf.isFeatureFlagKnown(flag) {
-			return nil, fmt.Errorf("Unsupported feature flag %q", flag)
-		}
-	}
-
-	// Check that all required feature flags are set
-	var requiredFlags []flagIota
-	if cf.IsFeatureFlagSet(FlagPlaintextNames) {
-		requiredFlags = requiredFlagsPlaintextNames
-	} else {
-		requiredFlags = requiredFlagsNormal
-	}
-	deprecatedFs := false
-	for _, i := range requiredFlags {
-		if !cf.IsFeatureFlagSet(i) {
-			fmt.Fprintf(os.Stderr, "Required feature flag %q is missing\n", knownFlags[i])
-			deprecatedFs = true
-		}
-	}
-	if deprecatedFs {
-		return nil, exitcodes.NewErr("Deprecated filesystem", exitcodes.DeprecatedFS)
+	if err := cf.Validate(); err != nil {
+		return nil, exitcodes.NewErr(err.Error(), exitcodes.DeprecatedFS)
 	}
 
 	// All good
 	return &cf, nil
 }
 
+func (cf *ConfFile) setFeatureFlag(flag flagIota) {
+	if cf.IsFeatureFlagSet(flag) {
+		// Already set, ignore
+		return
+	}
+	cf.FeatureFlags = append(cf.FeatureFlags, knownFlags[flag])
+}
+
 // DecryptMasterKey decrypts the masterkey stored in cf.EncryptedKey using
 // password.
 func (cf *ConfFile) DecryptMasterKey(password []byte, giveHash bool) (masterkey, scryptHash []byte, err error) {
@@ -296,6 +279,9 @@ func (cf *ConfFile) GetMasterkey(password, givenScryptHash, returnedScryptHashBu
 // then rename over "filename".
 // This way a password change atomically replaces the file.
 func (cf *ConfFile) WriteFile() error {
+	if err := cf.Validate(); err != nil {
+		return err
+	}
 	tmp := cf.filename + ".tmp"
 	// 0400 permissions: gocryptfs.conf should be kept secret and never be written to.
 	fd, err := os.OpenFile(tmp, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0400)
@@ -315,7 +301,7 @@ func (cf *ConfFile) WriteFile() error {
 	err = fd.Sync()
 	if err != nil {
 		// This can happen on network drives: FRITZ.NAS mounted on MacOS returns
-		// "operation not supported": https://github.com/rfjakob/gocryptfs/issues/390
+		// "operation not supported": https://github.com/rfjakob/gocryptfs/v2/issues/390
 		// Try sync instead
 		syscall.Sync()
 	}
@@ -340,3 +326,18 @@ func getKeyEncrypter(scryptHash []byte, useHKDF bool) *contentenc.ContentEnc {
 	ce := contentenc.New(cc, 4096, false)
 	return ce
 }
+
+// ContentEncryption tells us which content encryption algorithm is selected
+func (cf *ConfFile) ContentEncryption() (algo cryptocore.AEADTypeEnum, err error) {
+	if err := cf.Validate(); err != nil {
+		return cryptocore.AEADTypeEnum{}, err
+	}
+	if cf.IsFeatureFlagSet(FlagXChaCha20Poly1305) {
+		return cryptocore.BackendXChaCha20Poly1305, nil
+	}
+	if cf.IsFeatureFlagSet(FlagAESSIV) {
+		return cryptocore.BackendAESSIV, nil
+	}
+	// If neither AES-SIV nor XChaCha are selected, we must be using AES-GCM
+	return cryptocore.BackendGoGCM, nil
+}
diff --git a/internal/configfile/feature_flags.go b/internal/configfile/feature_flags.go
index 5964a53..e28abd6 100644
--- a/internal/configfile/feature_flags.go
+++ b/internal/configfile/feature_flags.go
@@ -11,7 +11,8 @@ const (
 	// This flag is mandatory since gocryptfs v1.0.
 	FlagEMENames
 	// FlagGCMIV128 indicates 128-bit GCM IVs.
-	// This flag is mandatory since gocryptfs v1.0.
+	// This flag is mandatory since gocryptfs v1.0,
+	// except when XChaCha20Poly1305 is used.
 	FlagGCMIV128
 	// FlagLongNames allows file names longer than 176 bytes.
 	FlagLongNames
@@ -28,36 +29,26 @@ const (
 	// FlagFIDO2 means that "-fido2" was used when creating the filesystem.
 	// The masterkey is protected using a FIDO2 token instead of a password.
 	FlagFIDO2
+	// FlagXChaCha20Poly1305 means we use XChaCha20-Poly1305 file content encryption
+	FlagXChaCha20Poly1305
 )
 
 // knownFlags stores the known feature flags and their string representation
 var knownFlags = map[flagIota]string{
-	FlagPlaintextNames: "PlaintextNames",
-	FlagDirIV:          "DirIV",
-	FlagEMENames:       "EMENames",
-	FlagGCMIV128:       "GCMIV128",
-	FlagLongNames:      "LongNames",
-	FlagAESSIV:         "AESSIV",
-	FlagRaw64:          "Raw64",
-	FlagHKDF:           "HKDF",
-	FlagFIDO2:          "FIDO2",
-}
-
-// Filesystems that do not have these feature flags set are deprecated.
-var requiredFlagsNormal = []flagIota{
-	FlagDirIV,
-	FlagEMENames,
-	FlagGCMIV128,
-}
-
-// Filesystems without filename encryption obviously don't have or need the
-// filename related feature flags.
-var requiredFlagsPlaintextNames = []flagIota{
-	FlagGCMIV128,
+	FlagPlaintextNames:    "PlaintextNames",
+	FlagDirIV:             "DirIV",
+	FlagEMENames:          "EMENames",
+	FlagGCMIV128:          "GCMIV128",
+	FlagLongNames:         "LongNames",
+	FlagAESSIV:            "AESSIV",
+	FlagRaw64:             "Raw64",
+	FlagHKDF:              "HKDF",
+	FlagFIDO2:             "FIDO2",
+	FlagXChaCha20Poly1305: "XChaCha20Poly1305",
 }
 
 // isFeatureFlagKnown verifies that we understand a feature flag.
-func (cf *ConfFile) isFeatureFlagKnown(flag string) bool {
+func isFeatureFlagKnown(flag string) bool {
 	for _, knownFlag := range knownFlags {
 		if knownFlag == flag {
 			return true
diff --git a/internal/configfile/scrypt.go b/internal/configfile/scrypt.go
index c1edf4b..8178a92 100644
--- a/internal/configfile/scrypt.go
+++ b/internal/configfile/scrypt.go
@@ -1,6 +1,7 @@
 package configfile
 
 import (
+	"fmt"
 	"log"
 	"math"
 	"os"
@@ -61,8 +62,9 @@ func NewScryptKDF(logN int) ScryptKDF {
 
 // DeriveKey returns a new key from a supplied password.
 func (s *ScryptKDF) DeriveKey(pw []byte) []byte {
-	s.validateParams()
-
+	if err := s.validateParams(); err != nil {
+		os.Exit(exitcodes.ScryptParams)
+	}
 	k, err := scrypt.Key(pw, s.Salt, s.N, s.R, s.P, s.KeyLen)
 	if err != nil {
 		log.Panicf("DeriveKey failed: %v", err)
@@ -80,21 +82,22 @@ func (s *ScryptKDF) LogN() int {
 // If not, it exists with an error message.
 // This makes sure we do not get weak parameters passed through a
 // rougue gocryptfs.conf.
-func (s *ScryptKDF) validateParams() {
+func (s *ScryptKDF) validateParams() error {
 	minN := 1 << scryptMinLogN
 	if s.N < minN {
-		os.Exit(exitcodes.ScryptParams)
+		return fmt.Errorf("Fatal: scryptn below 10 is too low to make sense")
 	}
 	if s.R < scryptMinR {
-		os.Exit(exitcodes.ScryptParams)
+		return fmt.Errorf("Fatal: scrypt parameter R below minimum: value=%d, min=%d", s.R, scryptMinR)
 	}
 	if s.P < scryptMinP {
-		os.Exit(exitcodes.ScryptParams)
+		return fmt.Errorf("Fatal: scrypt parameter P below minimum: value=%d, min=%d", s.P, scryptMinP)
 	}
 	if len(s.Salt) < scryptMinSaltLen {
-		os.Exit(exitcodes.ScryptParams)
+		return fmt.Errorf("Fatal: scrypt salt length below minimum: value=%d, min=%d", len(s.Salt), scryptMinSaltLen)
 	}
 	if s.KeyLen < cryptocore.KeyLen {
-		os.Exit(exitcodes.ScryptParams)
+		return fmt.Errorf("Fatal: scrypt parameter KeyLen below minimum: value=%d, min=%d", s.KeyLen, cryptocore.KeyLen)
 	}
+	return nil
 }
diff --git a/internal/configfile/validate.go b/internal/configfile/validate.go
new file mode 100644
index 0000000..6bd4f3b
--- /dev/null
+++ b/internal/configfile/validate.go
@@ -0,0 +1,67 @@
+package configfile
+
+import (
+	"fmt"
+
+	"../contentenc"
+)
+
+// Validate that the combination of settings makes sense and is supported
+func (cf *ConfFile) Validate() error {
+	if cf.Version != contentenc.CurrentVersion {
+		return fmt.Errorf("Unsupported on-disk format %d", cf.Version)
+	}
+	// scrypt params ok?
+	if err := cf.ScryptObject.validateParams(); err != nil {
+		return err
+	}
+	// All feature flags that are in the config file are known?
+	for _, flag := range cf.FeatureFlags {
+		if !isFeatureFlagKnown(flag) {
+			return fmt.Errorf("Unknown feature flag %q", flag)
+		}
+	}
+	// File content encryption
+	{
+		switch {
+		case cf.IsFeatureFlagSet(FlagXChaCha20Poly1305) && cf.IsFeatureFlagSet(FlagAESSIV):
+			return fmt.Errorf("Can't have both XChaCha20Poly1305 and AESSIV feature flags")
+		case cf.IsFeatureFlagSet(FlagAESSIV):
+			if !cf.IsFeatureFlagSet(FlagGCMIV128) {
+				return fmt.Errorf("AESSIV requires GCMIV128 feature flag")
+			}
+		case cf.IsFeatureFlagSet(FlagXChaCha20Poly1305):
+			if cf.IsFeatureFlagSet(FlagGCMIV128) {
+				return fmt.Errorf("XChaCha20Poly1305 conflicts with GCMIV128 feature flag")
+			}
+			if !cf.IsFeatureFlagSet(FlagHKDF) {
+				return fmt.Errorf("XChaCha20Poly1305 requires HKDF feature flag")
+			}
+		// The absence of other flags means AES-GCM (oldest algorithm)
+		case !cf.IsFeatureFlagSet(FlagXChaCha20Poly1305) && !cf.IsFeatureFlagSet(FlagAESSIV):
+			if !cf.IsFeatureFlagSet(FlagGCMIV128) {
+				return fmt.Errorf("AES-GCM requires GCMIV128 feature flag")
+			}
+		}
+	}
+	// Filename encryption
+	{
+		switch {
+		case cf.IsFeatureFlagSet(FlagPlaintextNames) && cf.IsFeatureFlagSet(FlagEMENames):
+			return fmt.Errorf("Can't have both PlaintextNames and EMENames feature flags")
+		case cf.IsFeatureFlagSet(FlagPlaintextNames):
+			if cf.IsFeatureFlagSet(FlagDirIV) {
+				return fmt.Errorf("PlaintextNames conflicts with DirIV feature flag")
+			}
+			if cf.IsFeatureFlagSet(FlagLongNames) {
+				return fmt.Errorf("PlaintextNames conflicts with LongNames feature flag")
+			}
+			if cf.IsFeatureFlagSet(FlagRaw64) {
+				return fmt.Errorf("PlaintextNames conflicts with Raw64 feature flag")
+			}
+		case cf.IsFeatureFlagSet(FlagEMENames):
+			// All combinations of DirIV, LongNames, Raw64 allowed
+		}
+	}
+	return nil
+}
diff --git a/internal/contentenc/content.go b/internal/contentenc/content.go
index c9b3c60..6b9fd41 100644
--- a/internal/contentenc/content.go
+++ b/internal/contentenc/content.go
@@ -13,9 +13,6 @@ import (
 	"../stupidgcm"
 )
 
-// NonceMode determines how nonces are created.
-type NonceMode int
-
 const (
 	//value from FUSE doc
 	MAX_KERNEL_WRITE = 128 * 1024
@@ -27,15 +24,6 @@ const (
 	// master key in the config file is encrypted with a 96-bit IV for
 	// gocryptfs v1.2 and earlier. v1.3 switched to 128 bit.
 	DefaultIVBits = 128
-
-	_ = iota // skip zero
-	// RandomNonce chooses a random nonce.
-	RandomNonce NonceMode = iota
-	// ReverseDeterministicNonce chooses a deterministic nonce, suitable for
-	// use in reverse mode.
-	ReverseDeterministicNonce NonceMode = iota
-	// ExternalNonce derives a nonce from external sources.
-	ExternalNonce NonceMode = iota
 )
 
 // ContentEnc is used to encipher and decipher file content.
@@ -171,7 +159,7 @@ func (be *ContentEnc) DecryptBlock(ciphertext []byte, blockNo uint64, fileID []b
 	nonce := ciphertext[:be.cryptoCore.IVLen]
 	if bytes.Equal(nonce, be.allZeroNonce) {
 		// Bug in tmpfs?
-		// https://github.com/rfjakob/gocryptfs/issues/56
+		// https://github.com/rfjakob/gocryptfs/v2/issues/56
 		// http://www.spinics.net/lists/kernel/msg2370127.html
 		return nil, errors.New("all-zero nonce")
 	}
diff --git a/internal/cryptocore/cryptocore.go b/internal/cryptocore/cryptocore.go
index 56e0baa..03e0416 100644
--- a/internal/cryptocore/cryptocore.go
+++ b/internal/cryptocore/cryptocore.go
@@ -6,10 +6,11 @@ import (
 	"crypto/aes"
 	"crypto/cipher"
 	"crypto/sha512"
-	"fmt"
 	"log"
 	"runtime"
 
+	"golang.org/x/crypto/chacha20poly1305"
+
 	"github.com/rfjakob/eme"
 
 	"../siv_aead"
@@ -17,37 +18,35 @@ import (
 )
 
 const (
-	// KeyLen is the cipher key length in bytes.  32 for AES-256.
+	// KeyLen is the cipher key length in bytes. All backends use 32 bytes.
 	KeyLen = 32
-	// AuthTagLen is the length of a GCM auth tag in bytes.
+	// AuthTagLen is the length of a authentication tag in bytes.
+	// All backends use 16 bytes.
 	AuthTagLen = 16
 )
 
 // AEADTypeEnum indicates the type of AEAD backend in use.
-type AEADTypeEnum int
-
-const (
-	// BackendOpenSSL specifies the OpenSSL backend.
-	BackendOpenSSL AEADTypeEnum = 3
-	// BackendGoGCM specifies the Go based GCM backend.
-	BackendGoGCM AEADTypeEnum = 4
-	// BackendAESSIV specifies an AESSIV backend.
-	BackendAESSIV AEADTypeEnum = 5
-)
-
-func (a AEADTypeEnum) String() string {
-	switch a {
-	case BackendOpenSSL:
-		return "BackendOpenSSL"
-	case BackendGoGCM:
-		return "BackendGoGCM"
-	case BackendAESSIV:
-		return "BackendAESSIV"
-	default:
-		return fmt.Sprintf("%d", a)
-	}
+type AEADTypeEnum struct {
+	Name      string
+	NonceSize int
 }
 
+// BackendOpenSSL specifies the OpenSSL backend.
+// "AES-GCM-256-OpenSSL" in gocryptfs -speed.
+var BackendOpenSSL AEADTypeEnum = AEADTypeEnum{"AES-GCM-256-OpenSSL", 16}
+
+// BackendGoGCM specifies the Go based GCM backend.
+// "AES-GCM-256-Go" in gocryptfs -speed.
+var BackendGoGCM AEADTypeEnum = AEADTypeEnum{"AES-GCM-256-Go", 16}
+
+// BackendAESSIV specifies an AESSIV backend.
+// "AES-SIV-512-Go" in gocryptfs -speed.
+var BackendAESSIV AEADTypeEnum = AEADTypeEnum{"AES-SIV-512-Go", siv_aead.NonceSize}
+
+// BackendXChaCha20Poly1305 specifies XChaCha20-Poly1305-Go.
+// "XChaCha20-Poly1305-Go" in gocryptfs -speed.
+var BackendXChaCha20Poly1305 AEADTypeEnum = AEADTypeEnum{"XChaCha20-Poly1305-Go", chacha20poly1305.NonceSizeX}
+
 // CryptoCore is the low level crypto implementation.
 type CryptoCore struct {
 	// EME is used for filename encryption.
@@ -58,7 +57,8 @@ type CryptoCore struct {
 	AEADBackend AEADTypeEnum
 	// GCM needs unique IVs (nonces)
 	IVGenerator *nonceGenerator
-	IVLen       int
+	// IVLen in bytes
+	IVLen int
 }
 
 // New returns a new CryptoCore object or panics.
@@ -71,10 +71,11 @@ type CryptoCore struct {
 // a config file) or the masterkey (when finally mounting the filesystem).
 func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDecode bool) *CryptoCore {
 	if len(key) != KeyLen {
-		log.Panic(fmt.Sprintf("Unsupported key length %d", len(key)))
+		log.Panicf("Unsupported key length of %d bytes", len(key))
+	}
+	if IVBitLen != 96 && IVBitLen != 128 && IVBitLen != chacha20poly1305.NonceSizeX*8 {
+		log.Panicf("Unsupported IV length of %d bits", IVBitLen)
 	}
-	// We want the IV size in bytes
-	IVLen := IVBitLen / 8
 
 	// Initialize EME for filename encryption.
 	var emeCipher *eme.EMECipher
@@ -103,12 +104,14 @@ func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDec
 		if useHKDF {
 			gcmKey = hkdfDerive(key, hkdfInfoGCMContent, KeyLen)
 		} else {
+			// Filesystems created by gocryptfs v0.7 through v1.2 don't use HKDF.
+			// Example: tests/example_filesystems/v0.9
 			gcmKey = append([]byte{}, key...)
 		}
 		switch aeadType {
 		case BackendOpenSSL:
-			if IVLen != 16 {
-				log.Panic("stupidgcm only supports 128-bit IVs")
+			if IVBitLen != 128 {
+				log.Panicf("stupidgcm only supports 128-bit IVs, you wanted %d", IVBitLen)
 			}
 			aeadCipher = stupidgcm.New(gcmKey, forceDecode)
 		case BackendGoGCM:
@@ -116,7 +119,7 @@ func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDec
 			if err != nil {
 				log.Panic(err)
 			}
-			aeadCipher, err = cipher.NewGCMWithNonceSize(goGcmBlockCipher, IVLen)
+			aeadCipher, err = cipher.NewGCMWithNonceSize(goGcmBlockCipher, IVBitLen/8)
 			if err != nil {
 				log.Panic(err)
 			}
@@ -125,9 +128,9 @@ func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDec
 			gcmKey[i] = 0
 		}
 	} else if aeadType == BackendAESSIV {
-		if IVLen != 16 {
-			// SIV supports any nonce size, but we only use 16.
-			log.Panic("AES-SIV must use 16-byte nonces")
+		if IVBitLen != 128 {
+			// SIV supports any nonce size, but we only use 128.
+			log.Panicf("AES-SIV must use 128-bit IVs, you wanted %d", IVBitLen)
 		}
 		// AES-SIV uses 1/2 of the key for authentication, 1/2 for
 		// encryption, so we need a 64-bytes key for AES-256. Derive it from
@@ -144,16 +147,34 @@ func New(key []byte, aeadType AEADTypeEnum, IVBitLen int, useHKDF bool, forceDec
 		for i := range key64 {
 			key64[i] = 0
 		}
+	} else if aeadType == BackendXChaCha20Poly1305 {
+		// We don't support legacy modes with XChaCha20-Poly1305
+		if IVBitLen != chacha20poly1305.NonceSizeX*8 {
+			log.Panicf("XChaCha20-Poly1305 must use 192-bit IVs, you wanted %d", IVBitLen)
+		}
+		if !useHKDF {
+			log.Panic("XChaCha20-Poly1305 must use HKDF, but it is disabled")
+		}
+		derivedKey := hkdfDerive(key, hkdfInfoXChaChaPoly1305Content, chacha20poly1305.KeySize)
+		aeadCipher, err = chacha20poly1305.NewX(derivedKey)
+		if err != nil {
+			log.Panic(err)
+		}
 	} else {
-		log.Panic("unknown backend cipher")
+		log.Panicf("unknown cipher backend %q", aeadType.Name)
+	}
+
+	if aeadCipher.NonceSize()*8 != IVBitLen {
+		log.Panicf("Mismatched aeadCipher.NonceSize*8=%d and IVBitLen=%d bits",
+			aeadCipher.NonceSize()*8, IVBitLen)
 	}
 
 	return &CryptoCore{
 		EMECipher:   emeCipher,
 		AEADCipher:  aeadCipher,
 		AEADBackend: aeadType,
-		IVGenerator: &nonceGenerator{nonceLen: IVLen},
-		IVLen:       IVLen,
+		IVGenerator: &nonceGenerator{nonceLen: IVBitLen / 8},
+		IVLen:       IVBitLen / 8,
 	}
 }
 
diff --git a/internal/cryptocore/hkdf.go b/internal/cryptocore/hkdf.go
index 87ca1b9..b56f507 100644
--- a/internal/cryptocore/hkdf.go
+++ b/internal/cryptocore/hkdf.go
@@ -10,9 +10,10 @@ import (
 const (
 	// "info" data that HKDF mixes into the generated key to make it unique.
 	// For convenience, we use a readable string.
-	hkdfInfoEMENames   = "EME filename encryption"
-	hkdfInfoGCMContent = "AES-GCM file content encryption"
-	hkdfInfoSIVContent = "AES-SIV file content encryption"
+	hkdfInfoEMENames               = "EME filename encryption"
+	hkdfInfoGCMContent             = "AES-GCM file content encryption"
+	hkdfInfoSIVContent             = "AES-SIV file content encryption"
+	hkdfInfoXChaChaPoly1305Content = "XChaCha20-Poly1305 file content encryption"
 )
 
 // hkdfDerive derives "outLen" bytes from "masterkey" and "info" using
diff --git a/internal/nametransform/diriv.go b/internal/nametransform/diriv.go
index ae46c9a..1e1e887 100644
--- a/internal/nametransform/diriv.go
+++ b/internal/nametransform/diriv.go
@@ -22,7 +22,11 @@ const (
 // ReadDirIVAt reads "gocryptfs.diriv" from the directory that is opened as "dirfd".
 // Using the dirfd makes it immune to concurrent renames of the directory.
 // Retries on EINTR.
-func ReadDirIVAt(dirfd int) (iv []byte, err error) {
+// If deterministicNames is set it returns an all-zero slice.
+func (n *NameTransform) ReadDirIVAt(dirfd int) (iv []byte, err error) {
+	if n.deterministicNames {
+		return make([]byte, DirIVLen), nil
+	}
 	fdRaw, err := syscallcompat.Openat(dirfd, DirIVFilename,
 		syscall.O_RDONLY|syscall.O_NOFOLLOW, 0)
 	if err != nil {
@@ -63,7 +67,7 @@ func WriteDirIVAt(dirfd int) error {
 	iv := cryptocore.RandBytes(DirIVLen)
 	// 0400 permissions: gocryptfs.diriv should never be modified after creation.
 	// Don't use "ioutil.WriteFile", it causes trouble on NFS:
-	// https://github.com/rfjakob/gocryptfs/commit/7d38f80a78644c8ec4900cc990bfb894387112ed
+	// https://github.com/rfjakob/gocryptfs/v2/commit/7d38f80a78644c8ec4900cc990bfb894387112ed
 	fd, err := syscallcompat.Openat(dirfd, DirIVFilename, os.O_WRONLY|os.O_CREATE|os.O_EXCL, dirivPerms)
 	if err != nil {
 		return err
diff --git a/internal/nametransform/longnames.go b/internal/nametransform/longnames.go
index 21e7714..4fc378e 100644
--- a/internal/nametransform/longnames.go
+++ b/internal/nametransform/longnames.go
@@ -124,7 +124,7 @@ func (n *NameTransform) WriteLongNameAt(dirfd int, hashName string, plainName st
 	plainName = filepath.Base(plainName)
 
 	// Encrypt the basename
-	dirIV, err := ReadDirIVAt(dirfd)
+	dirIV, err := n.ReadDirIVAt(dirfd)
 	if err != nil {
 		return err
 	}
diff --git a/internal/nametransform/names.go b/internal/nametransform/names.go
index 08ea41e..b631dd4 100644
--- a/internal/nametransform/names.go
+++ b/internal/nametransform/names.go
@@ -23,20 +23,22 @@ type NameTransform struct {
 	// on the Raw64 feature flag
 	B64 *base64.Encoding
 	// Patterns to bypass decryption
-	badnamePatterns []string
+	badnamePatterns    []string
+	deterministicNames bool
 }
 
 // New returns a new NameTransform instance.
-func New(e *eme.EMECipher, longNames bool, raw64 bool, badname []string) *NameTransform {
+func New(e *eme.EMECipher, longNames bool, raw64 bool, badname []string, deterministicNames bool) *NameTransform {
 	b64 := base64.URLEncoding
 	if raw64 {
 		b64 = base64.RawURLEncoding
 	}
 	return &NameTransform{
-		emeCipher:       e,
-		longNames:       longNames,
-		B64:             b64,
-		badnamePatterns: badname,
+		emeCipher:          e,
+		longNames:          longNames,
+		B64:                b64,
+		badnamePatterns:    badname,
+		deterministicNames: deterministicNames,
 	}
 }
 
diff --git a/internal/nametransform/perms.go b/internal/nametransform/perms.go
index cfcd062..6b88afd 100644
--- a/internal/nametransform/perms.go
+++ b/internal/nametransform/perms.go
@@ -6,14 +6,14 @@ const (
 	// never chmod'ed or chown'ed.
 	//
 	// Group-readable so the FS can be mounted by several users in the same group
-	// (see https://github.com/rfjakob/gocryptfs/issues/387 ).
+	// (see https://github.com/rfjakob/gocryptfs/v2/issues/387 ).
 	//
 	// Note that gocryptfs.conf is still created with 0400 permissions so the
 	// owner must explicitly chmod it to permit access.
 	//
 	// World-readable so an encrypted directory can be copied by the non-root
 	// owner when gocryptfs is running as root
-	// ( https://github.com/rfjakob/gocryptfs/issues/539 ).
+	// ( https://github.com/rfjakob/gocryptfs/v2/issues/539 ).
 	dirivPerms = 0444
 
 	// Permissions for gocryptfs.longname.[sha256].name files.
diff --git a/internal/siv_aead/siv_aead.go b/internal/siv_aead/siv_aead.go
index eabb5e2..482efd9 100644
--- a/internal/siv_aead/siv_aead.go
+++ b/internal/siv_aead/siv_aead.go
@@ -19,6 +19,11 @@ const (
 	// KeyLen is the required key length. The SIV algorithm supports other lengths,
 	// but we only support 64.
 	KeyLen = 64
+	// NonceSize is the required nonce/IV length.
+	// SIV supports any nonce size, but in gocryptfs we exclusively use 16.
+	NonceSize = 16
+	// Overhead is the number of bytes added for integrity checking
+	Overhead = 16
 )
 
 // New returns a new cipher.AEAD implementation.
@@ -42,11 +47,11 @@ func new2(keyIn []byte) cipher.AEAD {
 
 func (s *sivAead) NonceSize() int {
 	// SIV supports any nonce size, but in gocryptfs we exclusively use 16.
-	return 16
+	return NonceSize
 }
 
 func (s *sivAead) Overhead() int {
-	return 16
+	return Overhead
 }
 
 // Seal encrypts "in" using "nonce" and "authData" and appends the result to "dst"
diff --git a/internal/stupidgcm/prefer.go b/internal/stupidgcm/prefer.go
index bacd56a..94c1b6c 100644
--- a/internal/stupidgcm/prefer.go
+++ b/internal/stupidgcm/prefer.go
@@ -14,7 +14,7 @@ import (
 // 2) Is ARM64  && has AES instructions && Go is v1.11 or higher
 //    (commit https://github.com/golang/go/commit/4f1f503373cda7160392be94e3849b0c9b9ebbda)
 //
-// See https://github.com/rfjakob/gocryptfs/wiki/CPU-Benchmarks
+// See https://github.com/rfjakob/gocryptfs/v2/wiki/CPU-Benchmarks
 // for benchmarks.
 func PreferOpenSSL() bool {
 	if BuiltWithoutOpenssl {
@@ -26,7 +26,7 @@ func PreferOpenSSL() bool {
 		return false
 	}
 	// On the Apple M1, Go stdlib is faster than OpenSSL, despite cpu.ARM64.HasAES
-	// reading false: https://github.com/rfjakob/gocryptfs/issues/556#issuecomment-848079309
+	// reading false: https://github.com/rfjakob/gocryptfs/v2/issues/556#issuecomment-848079309
 	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
 		return false
 	}
diff --git a/internal/stupidgcm/stupidgcm.go b/internal/stupidgcm/stupidgcm.go
index 82d0323..01db41b 100644
--- a/internal/stupidgcm/stupidgcm.go
+++ b/internal/stupidgcm/stupidgcm.go
@@ -224,7 +224,7 @@ func (g *StupidGCM) Open(dst, iv, in, authData []byte) ([]byte, error) {
 	if res != 1 {
 		// The error code must always be checked by the calling function, because the decrypted buffer
 		// may contain corrupted data that we are returning in case the user forced reads
-		if g.forceDecode == true {
+		if g.forceDecode {
 			return append(dst, buf...), ErrAuth
 		}
 		return nil, ErrAuth
diff --git a/internal/stupidgcm/without_openssl.go b/internal/stupidgcm/without_openssl.go
deleted file mode 100644
index d420da3..0000000
--- a/internal/stupidgcm/without_openssl.go
+++ /dev/null
@@ -1,52 +0,0 @@
-// +build without_openssl
-
-package stupidgcm
-
-import (
-	"fmt"
-	"os"
-
-	"../exitcodes"
-)
-
-type StupidGCM struct{}
-
-const (
-	// BuiltWithoutOpenssl indicates if openssl been disabled at compile-time
-	BuiltWithoutOpenssl = true
-)
-
-func errExit() {
-	fmt.Fprintln(os.Stderr, "gocryptfs has been compiled without openssl support but you are still trying to use openssl")
-	os.Exit(exitcodes.OpenSSL)
-}
-
-func New(_ []byte, _ bool) *StupidGCM {
-	errExit()
-	// Never reached
-	return &StupidGCM{}
-}
-
-func (g *StupidGCM) NonceSize() int {
-	errExit()
-	return -1
-}
-
-func (g *StupidGCM) Overhead() int {
-	errExit()
-	return -1
-}
-
-func (g *StupidGCM) Seal(_, _, _, _ []byte) []byte {
-	errExit()
-	return nil
-}
-
-func (g *StupidGCM) Open(_, _, _, _ []byte) ([]byte, error) {
-	errExit()
-	return nil, nil
-}
-
-func (g *StupidGCM) Wipe() {
-	errExit()
-}
diff --git a/internal/syscallcompat/eintr.go b/internal/syscallcompat/eintr.go
index cdde806..2e2bb18 100644
--- a/internal/syscallcompat/eintr.go
+++ b/internal/syscallcompat/eintr.go
@@ -12,7 +12,7 @@ import (
 // https://github.com/golang/go/blob/d2a80f3fb5b44450e0b304ac5a718f99c053d82a/src/os/file_posix.go#L243
 //
 // This is needed because CIFS throws lots of EINTR errors:
-// https://github.com/rfjakob/gocryptfs/issues/483
+// https://github.com/rfjakob/gocryptfs/v2/issues/483
 //
 // Don't use retryEINTR() with syscall.Close()!
 // See https://code.google.com/p/chromium/issues/detail?id=269623 .
diff --git a/internal/syscallcompat/getdents_linux.go b/internal/syscallcompat/getdents_linux.go
index df886b4..5fa2a82 100644
--- a/internal/syscallcompat/getdents_linux.go
+++ b/internal/syscallcompat/getdents_linux.go
@@ -19,7 +19,7 @@ const sizeofDirent = int(unsafe.Sizeof(unix.Dirent{}))
 
 // maxReclen sanity check: Reclen should never be larger than this.
 // Due to padding between entries, it is 280 even on 32-bit architectures.
-// See https://github.com/rfjakob/gocryptfs/issues/197 for details.
+// See https://github.com/rfjakob/gocryptfs/v2/issues/197 for details.
 const maxReclen = 280
 
 type DirEntry struct {
diff --git a/internal/syscallcompat/sys_common.go b/internal/syscallcompat/sys_common.go
index 0123b25..ea9ac14 100644
--- a/internal/syscallcompat/sys_common.go
+++ b/internal/syscallcompat/sys_common.go
@@ -1,7 +1,6 @@
 package syscallcompat
 
 import (
-	"bytes"
 	"syscall"
 
 	"golang.org/x/sys/unix"
@@ -27,21 +26,6 @@ func Readlinkat(dirfd int, path string) (string, error) {
 	}
 }
 
-// Faccessat exists both in Linux and in MacOS 10.10+, but the Linux version
-// DOES NOT support any flags. Emulate AT_SYMLINK_NOFOLLOW like glibc does.
-func Faccessat(dirfd int, path string, mode uint32) error {
-	var st unix.Stat_t
-	err := Fstatat(dirfd, path, &st, unix.AT_SYMLINK_NOFOLLOW)
-	if err != nil {
-		return err
-	}
-	if st.Mode&syscall.S_IFMT == syscall.S_IFLNK {
-		// Pretend that a symlink is always accessible
-		return nil
-	}
-	return unix.Faccessat(dirfd, path, mode, 0)
-}
-
 // Openat wraps the Openat syscall.
 // Retries on EINTR.
 func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error) {
@@ -57,15 +41,6 @@ func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error)
 	return fd, err
 }
 
-// Fchownat syscall.
-func Fchownat(dirfd int, path string, uid int, gid int, flags int) (err error) {
-	// Why would we ever want to call this without AT_SYMLINK_NOFOLLOW?
-	if flags&unix.AT_SYMLINK_NOFOLLOW == 0 {
-		flags |= unix.AT_SYMLINK_NOFOLLOW
-	}
-	return unix.Fchownat(dirfd, path, uid, gid, flags)
-}
-
 // Fstatat syscall.
 // Retries on EINTR.
 func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error) {
@@ -100,118 +75,3 @@ const XATTR_BUFSZ = XATTR_SIZE_MAX + 1024
 
 // We try with a small buffer first - this one can be allocated on the stack.
 const XATTR_BUFSZ_SMALL = 500
-
-// Fgetxattr is a wrapper around unix.Fgetxattr that handles the buffer sizing.
-func Fgetxattr(fd int, attr string) (val []byte, err error) {
-	fn := func(buf []byte) (int, error) {
-		return unix.Fgetxattr(fd, attr, buf)
-	}
-	return getxattrSmartBuf(fn)
-}
-
-// Lgetxattr is a wrapper around unix.Lgetxattr that handles the buffer sizing.
-func Lgetxattr(path string, attr string) (val []byte, err error) {
-	fn := func(buf []byte) (int, error) {
-		return unix.Lgetxattr(path, attr, buf)
-	}
-	return getxattrSmartBuf(fn)
-}
-
-func getxattrSmartBuf(fn func(buf []byte) (int, error)) ([]byte, error) {
-	// Fastpaths. Important for security.capabilities, which gets queried a lot.
-	buf := make([]byte, XATTR_BUFSZ_SMALL)
-	sz, err := fn(buf)
-	// Non-existing xattr
-	if err == unix.ENODATA {
-		return nil, err
-	}
-	// Underlying fs does not support security.capabilities (example: tmpfs)
-	if err == unix.EOPNOTSUPP {
-		return nil, err
-	}
-	// Small xattr
-	if err == nil && sz < len(buf) {
-		goto out
-	}
-	// Generic slowpath
-	//
-	// If the buffer is too small to fit the value, Linux and MacOS react
-	// differently:
-	// Linux: returns an ERANGE error and "-1" bytes.
-	// MacOS: truncates the value and returns "size" bytes.
-	//
-	// We choose the simple approach of buffer that is bigger than the limit on
-	// Linux, and return an error for everything that is bigger (which can
-	// only happen on MacOS).
-	buf = make([]byte, XATTR_BUFSZ)
-	sz, err = fn(buf)
-	if err == syscall.ERANGE {
-		// Do NOT return ERANGE - the user might retry ad inifinitum!
-		return nil, syscall.EOVERFLOW
-	}
-	if err != nil {
-		return nil, err
-	}
-	if sz >= XATTR_SIZE_MAX {
-		return nil, syscall.EOVERFLOW
-	}
-out:
-	// Copy only the actually used bytes to a new (smaller) buffer
-	// so "buf" never leaves the function and can be allocated on the stack.
-	val := make([]byte, sz)
-	copy(val, buf)
-	return val, nil
-}
-
-// Flistxattr is a wrapper for unix.Flistxattr that handles buffer sizing and
-// parsing the returned blob to a string slice.
-func Flistxattr(fd int) (attrs []string, err error) {
-	// See the buffer sizing comments in getxattrSmartBuf.
-	// TODO: smarter buffer sizing?
-	buf := make([]byte, XATTR_BUFSZ)
-	sz, err := unix.Flistxattr(fd, buf)
-	if err == syscall.ERANGE {
-		// Do NOT return ERANGE - the user might retry ad inifinitum!
-		return nil, syscall.EOVERFLOW
-	}
-	if err != nil {
-		return nil, err
-	}
-	if sz >= XATTR_SIZE_MAX {
-		return nil, syscall.EOVERFLOW
-	}
-	attrs = parseListxattrBlob(buf[:sz])
-	return attrs, nil
-}
-
-// Llistxattr is a wrapper for unix.Llistxattr that handles buffer sizing and
-// parsing the returned blob to a string slice.
-func Llistxattr(path string) (attrs []string, err error) {
-	// TODO: smarter buffer sizing?
-	buf := make([]byte, XATTR_BUFSZ)
-	sz, err := unix.Llistxattr(path, buf)
-	if err == syscall.ERANGE {
-		// Do NOT return ERANGE - the user might retry ad inifinitum!
-		return nil, syscall.EOVERFLOW
-	}
-	if err != nil {
-		return nil, err
-	}
-	if sz >= XATTR_SIZE_MAX {
-		return nil, syscall.EOVERFLOW
-	}
-	attrs = parseListxattrBlob(buf[:sz])
-	return attrs, nil
-}
-
-func parseListxattrBlob(buf []byte) (attrs []string) {
-	parts := bytes.Split(buf, []byte{0})
-	for _, part := range parts {
-		if len(part) == 0 {
-			// Last part is empty, ignore
-			continue
-		}
-		attrs = append(attrs, string(part))
-	}
-	return attrs
-}
diff --git a/internal/syscallcompat/sys_linux.go b/internal/syscallcompat/sys_linux.go
index d0fa027..70beb5f 100644
--- a/internal/syscallcompat/sys_linux.go
+++ b/internal/syscallcompat/sys_linux.go
@@ -35,7 +35,7 @@ func EnospcPrealloc(fd int, off int64, len int64) (err error) {
 		}
 		if err == syscall.EOPNOTSUPP {
 			// ZFS and ext3 do not support fallocate. Warn but continue anyway.
-			// https://github.com/rfjakob/gocryptfs/issues/22
+			// https://github.com/rfjakob/gocryptfs/v2/issues/22
 			return nil
 		}
 		return err
diff --git a/volume.go b/volume.go
index 17e7658..52ff4d1 100644
--- a/volume.go
+++ b/volume.go
@@ -75,7 +75,7 @@ func registerNewVolume(rootCipherDir string, masterkey []byte, cf *configfile.Co
 	newVolume.cryptoCore = cryptocore.New(masterkey, cryptoBackend, contentenc.DefaultIVBits, true, forcedecode)
 	newVolume.contentEnc = contentenc.New(newVolume.cryptoCore, contentenc.DefaultBS, forcedecode)
 	var badname []string
-	newVolume.nameTransform = nametransform.New(newVolume.cryptoCore.EMECipher, true, true, badname)
+	newVolume.nameTransform = nametransform.New(newVolume.cryptoCore.EMECipher, true, true, badname, false)
 
 	//copying rootCipherDir
 	var grcd strings.Builder
@@ -156,7 +156,16 @@ func gcf_change_password(rootCipherDir string, oldPassword, givenScryptHash, new
 
 //export gcf_create_volume
 func gcf_create_volume(rootCipherDir string, password []byte, plaintextNames bool, logN int, creator string) bool {
-	err := configfile.Create(filepath.Join(rootCipherDir, configfile.ConfDefaultName), password, plaintextNames, logN, creator, false, false, nil, nil)
+	err := configfile.Create(&configfile.CreateArgs{
+		Filename:           filepath.Join(rootCipherDir, configfile.ConfDefaultName),
+		Password:           password,
+		PlaintextNames:     plaintextNames,
+		LogN:               logN,
+		Creator:            creator,
+		AESSIV:             false,
+		DeterministicNames: false,
+		XChaCha20Poly1305:  false,
+	})
 	if err == nil {
 		if plaintextNames {
 			return true