diff --git a/pkg/schema/blob.go b/pkg/schema/blob.go
index 88c5468bd..5a877b67e 100644
--- a/pkg/schema/blob.go
+++ b/pkg/schema/blob.go
@@ -132,7 +132,7 @@ func (b *Blob) AsShare() (s Share, ok bool) {
 	if !ok {
 		return
 	}
-	if b.ss.Type == "share" && b.ss.AuthType == ShareHaveRef && b.ss.Target != nil {
+	if b.ss.ClaimType == claimTypeShare && b.ss.AuthType == ShareHaveRef && b.ss.Target != nil {
 		return Share{c}, true
 	}
 	return
@@ -161,17 +161,19 @@ func (b *Blob) StaticSetMembers() []*blobref.BlobRef {
 }
 
 func (b *Blob) ShareAuthType() string {
-	if b.Type() != "share" {
+	s, ok := b.AsShare()
+	if !ok {
 		return ""
 	}
-	return b.ss.AuthType
+	return s.AuthType()
 }
 
 func (b *Blob) ShareTarget() *blobref.BlobRef {
-	if b.Type() != "share" {
+	s, ok := b.AsShare()
+	if !ok {
 		return nil
 	}
-	return b.ss.Target
+	return s.Target()
 }
 
 // ModTime returns the "unixMtime" field, or the zero time.
@@ -210,9 +212,14 @@ type Share struct {
 	Claim
 }
 
+// AuthType returns the AuthType of the Share.
+func (s Share) AuthType() string {
+	return s.b.ss.AuthType
+}
+
 // Target returns the blob referenced by the Share.
 func (s Share) Target() *blobref.BlobRef {
-	return s.b.ShareTarget()
+	return s.b.ss.Target
 }
 
 // IsTransitive returns whether the Share transitively
diff --git a/pkg/schema/schema.go b/pkg/schema/schema.go
index c577e28c5..d05a3c7ad 100644
--- a/pkg/schema/schema.go
+++ b/pkg/schema/schema.go
@@ -636,14 +636,6 @@ func newBytes() *Builder {
 	return base(1, "bytes")
 }
 
-func NewShareRef(authType string, target *blobref.BlobRef, transitive bool) *Builder {
-	bb := base(1, "share")
-	bb.m["authType"] = authType
-	bb.m["target"] = target.String()
-	bb.m["transitive"] = transitive
-	return bb
-}
-
 type ClaimType string
 
 const (
@@ -652,14 +644,24 @@ const (
 	DelAttribute ClaimType = "del-attribute"
 )
 
-type ClaimParam struct {
-	Permanode *blobref.BlobRef // modified permanode
-	Type      ClaimType
-	Attribute string // required
-	Value     string // optional if Type == DelAttribute
+const claimTypeShare = "share"
+
+// claimParam is used to populate a claim map when building a new claim
+type claimParam struct {
+	claimType ClaimType
+
+	// Params specific to *Attribute claims:
+	permanode *blobref.BlobRef // modified permanode
+	attribute string           // required
+	value     string           // optional if Type == DelAttribute
+
+	// Params specific to "share" claims:
+	authType   string
+	target     *blobref.BlobRef
+	transitive bool
 }
 
-func NewClaim(claims ...*ClaimParam) *Builder {
+func NewClaim(claims ...*claimParam) *Builder {
 	bb := base(1, "claim")
 	bb.SetClaimDate(time.Now())
 	if len(claims) == 1 {
@@ -678,38 +680,54 @@ func NewClaim(claims ...*ClaimParam) *Builder {
 	return bb
 }
 
-func populateClaimMap(m map[string]interface{}, cp *ClaimParam) {
-	m["claimType"] = string(cp.Type)
-	m["attribute"] = cp.Attribute
-	m["permaNode"] = cp.Permanode.String()
-	if !(cp.Type == DelAttribute && cp.Value == "") {
-		m["value"] = cp.Value
+func populateClaimMap(m map[string]interface{}, cp *claimParam) {
+	m["claimType"] = string(cp.claimType)
+	if cp.claimType != claimTypeShare {
+		m["permaNode"] = cp.permanode.String()
+		m["attribute"] = cp.attribute
+		if !(cp.claimType == DelAttribute && cp.value == "") {
+			m["value"] = cp.value
+		}
+	} else {
+		m["authType"] = cp.authType
+		m["target"] = cp.target.String()
+		m["transitive"] = cp.transitive
 	}
 }
 
+// NewShareRef creates a *Builder for a "share" claim.
+func NewShareRef(authType string, target *blobref.BlobRef, transitive bool) *Builder {
+	return NewClaim(&claimParam{
+		claimType:  claimTypeShare,
+		authType:   authType,
+		target:     target,
+		transitive: transitive,
+	})
+}
+
 func NewSetAttributeClaim(permaNode *blobref.BlobRef, attr, value string) *Builder {
-	return NewClaim(&ClaimParam{
-		Permanode: permaNode,
-		Type:      SetAttribute,
-		Attribute: attr,
-		Value:     value,
+	return NewClaim(&claimParam{
+		permanode: permaNode,
+		claimType: SetAttribute,
+		attribute: attr,
+		value:     value,
 	})
 }
 
 func NewAddAttributeClaim(permaNode *blobref.BlobRef, attr, value string) *Builder {
-	return NewClaim(&ClaimParam{
-		Permanode: permaNode,
-		Type:      AddAttribute,
-		Attribute: attr,
-		Value:     value,
+	return NewClaim(&claimParam{
+		permanode: permaNode,
+		claimType: AddAttribute,
+		attribute: attr,
+		value:     value,
 	})
 }
 
 func NewDelAttributeClaim(permaNode *blobref.BlobRef, attr string) *Builder {
-	return NewClaim(&ClaimParam{
-		Permanode: permaNode,
-		Type:      DelAttribute,
-		Attribute: attr,
+	return NewClaim(&claimParam{
+		permanode: permaNode,
+		claimType: DelAttribute,
+		attribute: attr,
 	})
 }
 
diff --git a/pkg/schema/schema_test.go b/pkg/schema/schema_test.go
index 895e294cb..5bf7e56c3 100644
--- a/pkg/schema/schema_test.go
+++ b/pkg/schema/schema_test.go
@@ -170,20 +170,20 @@ func TestAttribute(t *testing.T) {
 }`,
 		},
 		{
-			bb: NewClaim(&ClaimParam{
-				Permanode: br,
-				Type:      SetAttribute,
-				Attribute: "foo",
-				Value:     "bar",
-			}, &ClaimParam{
-				Permanode: br,
-				Type:      DelAttribute,
-				Attribute: "foo",
-				Value:     "specific-del",
-			}, &ClaimParam{
-				Permanode: br,
-				Type:      DelAttribute,
-				Attribute: "foo",
+			bb: NewClaim(&claimParam{
+				permanode: br,
+				claimType: SetAttribute,
+				attribute: "foo",
+				value:     "bar",
+			}, &claimParam{
+				permanode: br,
+				claimType: DelAttribute,
+				attribute: "foo",
+				value:     "specific-del",
+			}, &claimParam{
+				permanode: br,
+				claimType: DelAttribute,
+				attribute: "foo",
 			}),
 			want: `{"camliVersion": 1,
   "camliType": "claim",