diff --git a/ast/builtins.go b/ast/builtins.go
index cfebe12a19..efbe88324d 100644
--- a/ast/builtins.go
+++ b/ast/builtins.go
@@ -109,6 +109,9 @@ var DefaultBuiltins = [...]*Builtin{
 	Date,
 	Clock,
 
+	// Crypto
+	CryptoX509ParseCertificates,
+
 	// Graphs
 	WalkBuiltin,
 
@@ -771,6 +774,21 @@ var Clock = &Builtin{
 	),
 }
 
+/**
+ * Crypto.
+ */
+
+// CryptoX509ParseCertificates returns one or more certificates from the given
+// base64 encoded string containing DER encoded certificates that have been
+// concatenated.
+var CryptoX509ParseCertificates = &Builtin{
+	Name: "crypto.x509.parse_certificates",
+	Decl: types.NewFunction(
+		types.Args(types.S),
+		types.NewArray(nil, types.NewObject(nil, types.NewDynamicProperty(types.S, types.A))),
+	),
+}
+
 /**
  * Graphs.
  */
diff --git a/docs/book/language-reference.md b/docs/book/language-reference.md
index 31e5133b2e..12326a3f94 100644
--- a/docs/book/language-reference.md
+++ b/docs/book/language-reference.md
@@ -125,6 +125,12 @@ The input `string` is a JSON Web Token encoded with JWS Compact Serialization. J
 > Multiple calls to the `time.now_ns` built-in function within a single policy
 evaluation query will always return the same value.
 
+### <a name="Cryptography"/>Cryptography
+
+| Built-in | Inputs | Description |
+| -------- | ------ | ----------- |
+| <span class="opa-keep-it-together">``crypto.x509.parse_certificates(string, array[object])``</span> | 1 | ``output`` is an array of X.509 certificates represented as JSON objects. |
+
 ### <a name="graphs"/>Graphs
 
 | Built-in | Inputs | Description |
diff --git a/topdown/crypto.go b/topdown/crypto.go
new file mode 100644
index 0000000000..66afd4b258
--- /dev/null
+++ b/topdown/crypto.go
@@ -0,0 +1,43 @@
+// Copyright 2018 The OPA Authors.  All rights reserved.
+// Use of this source code is governed by an Apache2
+// license that can be found in the LICENSE file.
+
+package topdown
+
+import (
+	"crypto/x509"
+	"encoding/json"
+
+	"github.com/open-policy-agent/opa/ast"
+	"github.com/open-policy-agent/opa/util"
+)
+
+func builtinCryptoX509ParseCertificates(a ast.Value) (ast.Value, error) {
+
+	str, err := builtinBase64Decode(a)
+	if err != nil {
+		return nil, err
+	}
+
+	certs, err := x509.ParseCertificates([]byte(str.(ast.String)))
+	if err != nil {
+		return nil, err
+	}
+
+	bs, err := json.Marshal(certs)
+	if err != nil {
+		return nil, err
+	}
+
+	var x interface{}
+
+	if err := util.UnmarshalJSON(bs, &x); err != nil {
+		return nil, err
+	}
+
+	return ast.InterfaceToValue(x)
+}
+
+func init() {
+	RegisterFunctionalBuiltin1(ast.CryptoX509ParseCertificates.Name, builtinCryptoX509ParseCertificates)
+}
diff --git a/topdown/crypto_test.go b/topdown/crypto_test.go
new file mode 100644
index 0000000000..d278ee9e3d
--- /dev/null
+++ b/topdown/crypto_test.go
@@ -0,0 +1,60 @@
+// Copyright 2018 The OPA Authors.  All rights reserved.
+// Use of this source code is governed by an Apache2
+// license that can be found in the LICENSE file.
+
+package topdown
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestCryptoX509ParseCertificates(t *testing.T) {
+
+	rule := `
+		p[x] {
+			parsed := crypto.x509.parse_certificates(certs)
+			x := oid_to_string(parsed[_].Issuer.Names[_].Type)
+		}
+	`
+
+	tests := []struct {
+		note     string
+		certs    string
+		rule     string
+		expected interface{}
+	}{
+		{
+			note:     "one",
+			certs:    `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`,
+			rule:     rule,
+			expected: `["2.5.4.6", "2.5.4.10", "2.5.4.3"]`,
+		},
+		{
+			note:     "multiple",
+			certs:    `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`,
+			rule:     rule,
+			expected: `["2.5.4.10", "2.5.4.11", "2.5.4.3", "2.5.4.6"]`,
+		},
+		{
+			note:     "bad",
+			certs:    `YmFkc3RyaW5n`,
+			rule:     rule,
+			expected: fmt.Errorf("asn1: structure error"),
+		},
+	}
+
+	data := loadSmallTestData()
+
+	for _, tc := range tests {
+		rules := []string{
+			fmt.Sprintf("certs = %q { true }", tc.certs),
+			fmt.Sprintf(`
+				oid_to_string(oid) = concat(".", [s | s := format_int(oid[_], 10)]) { true }
+			`),
+			tc.rule,
+		}
+		runTopDownTestCase(t, data, tc.note, rules, tc.expected)
+	}
+
+}