1 files changed, 57 insertions, 0 deletions
diff --git a/internal/cryptocore/cryptocore.go b/internal/cryptocore/cryptocore.go
new file mode 100644
index 0000000..f286896
--- /dev/null
+++ b/internal/cryptocore/cryptocore.go
@@ -0,0 +1,57 @@
+package cryptocore
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"fmt"
+)
+
+const (
+	KeyLen     = 32 // AES-256
+	AuthTagLen = 16
+)
+
+type CryptoCore struct {
+	BlockCipher cipher.Block
+	Gcm         cipher.AEAD
+	GcmIVGen    *nonceGenerator
+	IVLen       int
+}
+
+// "New" returns a new CryptoCore object or panics.
+func New(key []byte, useOpenssl bool, GCMIV128 bool) *CryptoCore {
+
+	if len(key) != KeyLen {
+		panic(fmt.Sprintf("Unsupported key length %d", len(key)))
+	}
+
+	// We want the IV size in bytes
+	IVLen := 96 / 8
+	if GCMIV128 {
+		IVLen = 128 / 8
+	}
+
+	// We always use built-in Go crypto for blockCipher because it is not
+	// performance-critical.
+	blockCipher, err := aes.NewCipher(key)
+	if err != nil {
+		panic(err)
+	}
+
+	var gcm cipher.AEAD
+	if useOpenssl {
+		gcm = opensslGCM{key}
+	} else {
+		gcm, err = goGCMWrapper(blockCipher, IVLen)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	return &CryptoCore{
+		BlockCipher: blockCipher,
+		Gcm:         gcm,
+		GcmIVGen:    &nonceGenerator{nonceLen: IVLen},
+		IVLen:       IVLen,
+	}
+}