add base files

lib/crypto/hmac.go

@@ -0,0 +1,43 @@
+package crypto
+
+import (
+  "crypto/md5"
+)
+
+const IPAD = byte(0x36)
+const OPAD = byte(0x5C)
+
+type HMACKey [32]byte
+type HMACDigest [16]byte
+
+func (hk HMACKey) xor(p byte) (i []byte) {
+  i = make([]byte, 64)
+  for idx, b := range hk {
+    i[idx] =  b ^ p
+  }
+  c := 32
+  for c > 0 {
+    c--
+    i[c+32] = p
+  }
+  return 
+}
+
+//
+// do i2p hmac 
+//
+func I2PHMAC(data []byte, k HMACKey) (d HMACDigest) {
+  
+  buff := make([]byte, 64+len(data))
+  ip := k.xor(IPAD)
+  copy(buff, ip)
+  copy(buff[64:], data)
+  h := md5.Sum(buff)
+
+  buff = make([]byte, 96)
+  copy(buff, k.xor(OPAD))
+  copy(buff[64:], h[:])
+  // go zeros slices so we do not have to zero
+  d = md5.Sum(buff)
+  return
+}