diff --git a/backend.go b/backend.go
index 226a7fd..184f001 100644
--- a/backend.go
+++ b/backend.go
@@ -8,6 +8,8 @@ import "encoding/hex"
 import "fmt"
 import "strings"
 import "net"
+import "github.com/hlandau/ncdns/namecoin"
+import "github.com/hlandau/ncdns/ncerr"
 
 type Backend interface {
   // Lookup all resource records having a given fully-qualified owner name,
@@ -25,7 +27,7 @@ type Backend interface {
 
 type ncBackend struct {
   s *Server
-  nc NamecoinConn
+  nc namecoin.NamecoinConn
   cache lru.Cache // items are of type *Domain
 }
 
@@ -125,7 +127,7 @@ func (tx *Btx) determineDomain() (subname, basename, rootname string, err error)
   parts := strings.Split(qname, ".")
   if len(parts) < 2 {
     if parts[0] != "bit" {
-      err = ErrNotInZone
+      err = ncerr.ErrNotInZone
       return
     }
 
@@ -150,7 +152,7 @@ func (tx *Btx) determineDomain() (subname, basename, rootname string, err error)
     }
   }
 
-  err = ErrNotInZone
+  err = ncerr.ErrNotInZone
   return
 }
 
@@ -165,7 +167,7 @@ func (tx *Btx) Do() (rrs []dns.RR, err error) {
 
   if tx.rootname == "" {
     // REFUSED
-    return nil, ErrNotInZone
+    return nil, ncerr.ErrNotInZone
   }
 
   if tx.subname == "" && tx.basename == "" {
@@ -272,7 +274,7 @@ func (tx *Btx) doUserDomain() (rrs []dns.RR, err error) {
 
 func (tx *Btx) doUnderDomain(d *Domain) (rrs []dns.RR, err error) {
   rrs, err = tx.addAnswersUnderNCValue(d.ncv, tx.subname)
-  if err == ErrNoResults {
+  if err == ncerr.ErrNoResults {
     err = nil
   }
 
@@ -315,14 +317,14 @@ func (tx *Btx) _findNCValue(ncv *ncValue, isubname, subname string, depth int,
     if !ok {
       sub, ok = ncv.Map["*"]
       if !ok {
-        return nil, "", ErrNoSuchDomain
+        return nil, "", ncerr.ErrNoSuchDomain
       }
     }
     return tx._findNCValue(sub, rest, head + "." + subname, depth+1, shortCircuitFunc)
   }
 
   if shortCircuitFunc != nil {
-    return nil, subname, ErrNoSuchDomain
+    return nil, subname, ncerr.ErrNoSuchDomain
   }
 
   return ncv, subname, nil
@@ -493,16 +495,6 @@ func (ncv *ncValue) GetDSs() (dss []dns.DS, err error) {
 // f[b]("a", "b.c.d.e.f.g.zzz.bit")
 // f[a]("", "a.b.c.d.e.f.g.zzz.bit")
 
-func absname(n string) string {
-  if n == "" {
-    return "."
-  }
-  if n[len(n)-1] != '.' {
-    return n + "."
-  }
-  return n
-}
-
 // Do low-level queries against an abstract zone file.
 func (b *ncBackend) Lookup(qname string) (rrs []dns.RR, err error) {
   btx := &Btx{}
diff --git a/namecoin.go b/namecoin/namecoin.go
similarity index 93%
rename from namecoin.go
rename to namecoin/namecoin.go
index a0fa33d..8b60d6f 100644
--- a/namecoin.go
+++ b/namecoin/namecoin.go
@@ -1,10 +1,14 @@
-package main
+package namecoin
+
+// btcjson had to be modified a bit to get correct error reporting.
 import "github.com/hlandauf/btcjson"
+import "github.com/hlandau/ncdns/ncerr"
+
 import "encoding/json"
 import "sync/atomic"
 import "fmt"
-//import "github.com/hlandau/degoutils/log"
 
+// Used for generating IDs for JSON-RPC requests.
 var idCounter int32 = 0
 
 func newID() int32 {
@@ -108,7 +112,7 @@ func (nc *NamecoinConn) Query(name string) (v string, err error) {
   if r.Error != nil {
     //log.Info("RPC error: ", r.Error)
     if r.Error.Code == -4 {
-        return "", ErrNoSuchDomain
+        return "", ncerr.ErrNoSuchDomain
     }
     return "", r.Error
   }
diff --git a/ncdns.go b/ncdns.go
index bb3f8f2..0698be2 100644
--- a/ncdns.go
+++ b/ncdns.go
@@ -8,6 +8,7 @@ import "fmt"
 import "strings"
 import "sort"
 import "github.com/hlandau/degoutils/config"
+import "github.com/hlandau/ncdns/ncerr"
 
 // A Go daemon to serve Namecoin domain records via DNS.
 // This daemon is intended to be used in one of the following situations:
@@ -161,10 +162,6 @@ func (s *Server) runListener(net string) *dns.Server {
   return ds
 }
 
-var ErrNoSuchDomain = rerrorf(dns.RcodeNameError, "no such domain")
-var ErrNotInZone = rerrorf(dns.RcodeRefused, "domain not in zone")
-var ErrNoResults = rerrorf(0, "no results")
-
 type Tx struct {
   req *dns.Msg
   res *dns.Msg
@@ -224,9 +221,9 @@ func (s *Server) handle(rw dns.ResponseWriter, reqMsg *dns.Msg) {
 
     err := tx.addAnswers()
     if err != nil {
-      if err == ErrNoResults {
+      if err == ncerr.ErrNoResults {
         tx.rcode = 0
-      } else if err == ErrNoSuchDomain {
+      } else if err == ncerr.ErrNoSuchDomain {
         tx.rcode = dns.RcodeNameError
       } else if tx.rcode == 0 {
         log.Infoe(err, "Handler error, doing SERVFAIL")
@@ -248,7 +245,7 @@ func (tx *Tx) blookup(qname string) (rrs []dns.RR, err error) {
   log.Info("blookup: ", qname)
   rrs, err = tx.s.b.Lookup(qname)
   if err == nil && len(rrs) == 0 {
-    err = ErrNoResults
+    err = ncerr.ErrNoResults
   }
   return
 }
@@ -380,7 +377,7 @@ A:
 
   if soa == nil {
     // If we didn't even get a SOA at any point, we don't have any appropriate zone for this query.
-    return ErrNotInZone
+    return ncerr.ErrNotInZone
   }
 
   tx.soa = soa
diff --git a/ncerr/ncerr.go b/ncerr/ncerr.go
new file mode 100644
index 0000000..6172bfa
--- /dev/null
+++ b/ncerr/ncerr.go
@@ -0,0 +1,35 @@
+package ncerr
+import "github.com/miekg/dns"
+import "fmt"
+
+// An Error interface which allows an associated rcode to be queried.
+type Error interface {
+  error
+  Rcode() int
+}
+
+type Rerr struct {
+  error
+  e error
+  rcode int
+}
+
+func (re *Rerr) Error() string {
+  return re.e.Error()
+}
+
+func (re *Rerr) Rcode() int {
+  return re.rcode
+}
+
+func rerrorf(rcode int, fmts string, args ...interface{}) Error {
+  re := &Rerr{}
+  re.e = fmt.Errorf(fmts, args...)
+  re.rcode = rcode
+  return re
+}
+
+// Standard errors.
+var ErrNoSuchDomain = rerrorf(dns.RcodeNameError, "no such domain")
+var ErrNotInZone = rerrorf(dns.RcodeRefused, "domain not in zone")
+var ErrNoResults = rerrorf(0, "no results")
diff --git a/util.go b/util.go
index 14cc09f..83434c2 100644
--- a/util.go
+++ b/util.go
@@ -6,6 +6,18 @@ import "github.com/miekg/dns"
 import "github.com/hlandau/degoutils/log"
 import "time"
 
+// miekg/dns demands a superflous trailing dot, this makes sure it is correctly appended.
+func absname(n string) string {
+  if n == "" {
+    return "."
+  }
+  if n[len(n)-1] != '.' {
+    return n + "."
+  }
+  return n
+}
+
+// Split a domain name a.b.c.d.e into parts a (the head) and b.c.d.e (the rest).
 func splitDomainHead(name string) (head string, rest string, err error) {
   parts := strings.Split(name, ".")
 
@@ -18,32 +30,25 @@ func splitDomainHead(name string) (head string, rest string, err error) {
   return
 }
 
-// unused
-func splitDomainName(name string) (parts []string) {
-  if len(name) == 0 {
-    return
-  }
-
-  if name[len(name)-1] == '.' {
-    name = name[0:len(name)-1]
-  }
-
-  parts = strings.Split(name, ".")
-
-  return
+// Determines if a transaction should be considered to have the given query type.
+// Returns true iff the query type was qtype or ANY.
+func (tx *Tx) istype(qtype uint16) bool {
+  return tx.qtype == qtype || tx.qtype == dns.TypeANY
 }
 
-func (tx *Tx) istype(x uint16) bool {
-  return tx.qtype == x || tx.qtype == dns.TypeANY
-}
-
-func stepName(n string) string {
-  if len(n) == 0 {
+// This is used in NSEC3 hash generation. A hash like ...decafbad has one added
+// to it so that it becomes ...decafbae. This is needed because NSEC3's hashes
+// are inclusive-exclusive (i.e. "[,)"), and we want a hash that covers only the
+// name specified.
+//
+// Takes a hash in base32hex form.
+func stepName(hashB32Hex string) string {
+  if len(hashB32Hex) == 0 {
     return ""
   }
 
-  b, err := base32.HexEncoding.DecodeString(n)
-  log.Panice(err, n)
+  b, err := base32.HexEncoding.DecodeString(hashB32Hex)
+  log.Panice(err, hashB32Hex)
 
   for i := len(b)-1; i>=0; i-- {
     b[i] += 1
@@ -55,8 +60,8 @@ func stepName(n string) string {
   return base32.HexEncoding.EncodeToString(b)
 }
 
+// Returns true iff a type should be covered by a RRSIG.
 func shouldSignType(t uint16, isAuthoritySection bool) bool {
-  //log.Info("shouldSignType ", t, " ", isAuthoritySection)
   switch t {
     case dns.TypeOPT:
       return false
@@ -67,6 +72,7 @@ func shouldSignType(t uint16, isAuthoritySection bool) bool {
   }
 }
 
+// Returns true iff a client requested DNSSEC.
 func (tx *Tx) useDNSSEC() bool {
   opt := tx.req.IsEdns0()
   if opt == nil {
@@ -75,38 +81,18 @@ func (tx *Tx) useDNSSEC() bool {
   return opt.Do()
 }
 
+// Sets an rcode for the response if there is no error rcode currently set for
+// the response. The idea is to return the rcode corresponding to the first
+// error which occurs.
 func (tx *Tx) setRcode(x int) {
   if tx.rcode == 0 {
     tx.rcode = x
   }
 }
 
-type Error interface {
-  error
-  Rcode() int
-}
-
-type Rerr struct {
-  error
-  e error
-  rcode int
-}
-
-func (re *Rerr) Error() string {
-  return re.e.Error()
-}
-
-func (re *Rerr) Rcode() int {
-  return re.rcode
-}
-
-func rerrorf(rcode int, fmts string, args ...interface{}) Error {
-  re := &Rerr{}
-  re.e = fmt.Errorf(fmts, args...)
-  re.rcode = rcode
-  return re
-}
 
+// Determines the maximum TTL for a slice of resource records.
+// Returns 0 if the slice is empty.
 func rraMaxTTL(rra []dns.RR) uint32 {
   x := uint32(0)
   for _, rr := range rra {
@@ -118,6 +104,7 @@ func rraMaxTTL(rra []dns.RR) uint32 {
   return x
 }
 
+// Used by signResponseSection.
 func (tx *Tx) signRRs(rra []dns.RR, useKSK bool) (dns.RR, error) {
   if len(rra) == 0 {
     return nil, fmt.Errorf("no RRs to such")
@@ -152,6 +139,7 @@ func (tx *Tx) signRRs(rra []dns.RR, useKSK bool) (dns.RR, error) {
   return rrsig, nil
 }
 
+// Used by signResponse.
 func (tx *Tx) signResponseSection(rra *[]dns.RR) error {
   if len(*rra) == 0 {
     return nil
@@ -202,6 +190,8 @@ func (tx *Tx) signResponseSection(rra *[]dns.RR) error {
   return nil
 }
 
+// This is called to append RRSIGs to the response based on the current records in the Answer and
+// Authority sections of the response. Records in the Additional section are not signed.
 func (tx *Tx) signResponse() error {
   if !tx.useDNSSEC() {
     return nil
@@ -219,6 +209,7 @@ func (tx *Tx) signResponse() error {
   return nil
 }
 
+// Used for sorting RRTYPE lists for encoding into type bit maps.
 type uint16Slice []uint16
 func (p uint16Slice) Len() int { return len(p) }
 func (p uint16Slice) Less(i, j int) bool { return p[i] < p[j] }