diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..81c0540
--- /dev/null
+++ b/index.d.ts
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+// Mapping of numeric id -> secret
+export type Keys = {[key: number]: string }
+
+export type Options = {
+  // The Encryption Algorithm, defaults to aes-128-cbc if unset
+  encryption?: "aes-128-cbc" | "aes-192-cbc" | "aes-256-cbc",
+
+  // Any random string that will append to the message when generating SHA1
+  digestSalt: string
+}
+
+export type Encryptor = {
+  encrypt: (data: string) => [encrypted: string, keyringId: string, digest: string];
+  decrypt: (encrypted: string, keyringId: string) => string;
+}
+
+/**
+ * Create a new keyring.
+ * A keyring is a combination of keys and functions for encryption/decryption.
+ *
+ * @public
+ * @param  {array}   keys                The encryption keys as described.
+ * @param  {Object}  options             The keyring options.
+ * @param  {String}  options.encryption  The encryption algorithm.
+ *                                       Can be `aes-128-cbc`, `aes-192-cbc` or `aes-256-cbc`.
+ * @param  {String}  options.digestSalt  Any random string that will be append to
+ *                                       the message when generating SHA1.
+ * @return {String}                      An object containing functions for encryption/decryption.
+ */
+export function keyring(keys: Keys, options?: Options): Encryptor;
+
+/**
+ * Generate a hash value for the given string in a hex-encoded form.
+ * @param  {String} value
+ * @return {String}        Hex-encoded string representing the SHA1 digest for the given string.
+ */
+export function sha1(value: string, options?: Options): string;