diff --git a/CHANGELOG.md b/CHANGELOG.md
index 629bbd0..e5b7b0b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # CHANGELOG
 
+## 2.0.0
+
+Signature related functions have changed to be asynchronous and to accept async
+functions as key retrieving functions
+
 ## 1.3.0
 
 asymmetric encryption and signatures
diff --git a/README.md b/README.md
index f8d9c5e..c820763 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # @sapphirecode/crypto-helper
 
-version: 1.3.x
+version: 2.0.x
 
 simple functions for cryptography
 
@@ -29,11 +29,11 @@ const check = crypto.checksum('foo'); // returns a sha 256 hex
 
 // jwt like object signing
 const signed = crypto.sign_object({foo: 'bar'}, 'secret');
-const info = crypto.get_signature_info(signed); // returns an object with iat (issued at), key_info and data
-const dec = crypto.decode_signed(signed); // decode a signed object without verifying the signature
-const ver = crypto.verify_signature(signed, 'secret', 10000); // verifies the signature and returns the contents. the timeout is in milliseconds and optional, timing will be ignored if omitted.
-const ver_info = crypto.verify_signature_get_info(signed, 'secret', 10000); // verify a signature and get signature information like iat and key_info
-const ver_func = crypto.verify_signature(
+const info = await crypto.get_signature_info(signed); // returns an object with iat (issued at), key_info and data
+const dec = await crypto.decode_signed(signed); // decode a signed object without verifying the signature
+const ver = await crypto.verify_signature(signed, 'secret', 10000); // verifies the signature and returns the contents. the timeout is in milliseconds and optional, timing will be ignored if omitted.
+const ver_info = await crypto.verify_signature_get_info(signed, 'secret', 10000); // verify a signature and get signature information like iat and key_info
+const ver_func = await crypto.verify_signature(
   signed,
   (signature_info) => 'secret',
   10000
diff --git a/lib/signatures.js b/lib/signatures.js
index 4614e89..6d69854 100644
--- a/lib/signatures.js
+++ b/lib/signatures.js
@@ -26,7 +26,14 @@ function sign_object (obj, key, key_info = null) {
   return res;
 }
 
-function parse_signature (str, key = null) {
+/**
+ * parse a string signature
+ *
+ * @param {string} str string to verify
+ * @param {string|((Object)=>string|Promise<string>)|null} key used key
+ * @returns {Promise<any>} returns object if successful, else null
+ */
+async function parse_signature (str, key = null) {
   let dec = str.split ('.');
   const version = dec[2];
   const res = {};
@@ -46,7 +53,7 @@ function parse_signature (str, key = null) {
   }
 
   if (key !== null) {
-    const string_key = typeof key === 'string' ? key : key (res.json);
+    const string_key = typeof key === 'string' ? key : await key (res.json);
     res.is_rsa = (/^-----BEGIN RSA PUBLIC KEY-----/u).test (string_key);
     res.hash = res.is_rsa
       ? asym_verify (dec[0], string_key, res.token)
@@ -59,18 +66,20 @@ function parse_signature (str, key = null) {
  * verify a signed object and return its info and contents
  *
  * @param {string} str string to verify
- * @param {string|(Object)=>string} key used key
- * @param {number|(Object)=>number} timeout timeout (optional)
- * @returns {any} returns object if successful, else null
+ * @param {string|((Object)=>string|Promise<string>)} key used key
+ * @param {number|((Object)=>number|Promise<number>)} timeout timeout (optional)
+ * @returns {Promise<any>} returns object if successful, else null
  */
-function verify_signature_get_info (str, key, timeout = 0) {
+async function verify_signature_get_info (str, key, timeout = 0) {
   if (typeof str !== 'string')
     return null;
-  const { json, token, hash, is_rsa } = parse_signature (str, key);
+  const { json, token, hash, is_rsa } = await parse_signature (str, key);
   if (is_rsa ? !hash : (token !== hash))
     return null;
   const time = Date.now () - json.iat;
-  const num_timeout = typeof timeout === 'number' ? timeout : timeout (json);
+  const num_timeout = typeof timeout === 'number'
+    ? timeout
+    : await timeout (json);
   if (num_timeout === 0 || time <= num_timeout)
     return json;
   return null;
@@ -80,12 +89,12 @@ function verify_signature_get_info (str, key, timeout = 0) {
  * verify a signed object and return its contents
  *
  * @param {string} str string to verify
- * @param {string|(Object)=>string} key used key
- * @param {number|(Object)=>number} timeout timeout (optional)
- * @returns {any} returns object if successful, else null
+ * @param {string|((Object)=>string|Promise<string>)} key used key
+ * @param {number|((Object)=>number|Promise<number>)} timeout timeout (optional)
+ * @returns {Promise<any>} returns object if successful, else null
  */
-function verify_signature (str, key, timeout = 0) {
-  const res = verify_signature_get_info (str, key, timeout);
+async function verify_signature (str, key, timeout = 0) {
+  const res = await verify_signature_get_info (str, key, timeout);
   if (res === null)
     return null;
   return res.obj;
@@ -95,12 +104,12 @@ function verify_signature (str, key, timeout = 0) {
  * get a signed object info and data
  *
  * @param {string} str string to decode
- * @returns {any} data
+ * @returns {Promise<any>} data
  */
-function get_signature_info (str) {
+async function get_signature_info (str) {
   if (typeof str !== 'string')
     return null;
-  const { json } = parse_signature (str);
+  const { json } = await parse_signature (str);
   return json;
 }
 
@@ -108,10 +117,10 @@ function get_signature_info (str) {
  * decode a signed object without verifying the signature
  *
  * @param {string} str string to decode
- * @returns {any} object
+ * @returns {Promise<any>} object
  */
-function decode_signed (str) {
-  const info = get_signature_info (str);
+async function decode_signed (str) {
+  const info = await get_signature_info (str);
   if (info)
     return info.obj;
   return null;
diff --git a/package.json b/package.json
index 3d31896..597862e 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@sapphirecode/crypto-helper",
-  "version": "1.3.0",
+  "version": "2.0.0",
   "main": "index.js",
   "author": {
     "name": "Timo Hocker",
diff --git a/test/spec/encryption.js b/test/spec/encryption.js
index 244d6b7..b4c59df 100644
--- a/test/spec/encryption.js
+++ b/test/spec/encryption.js
@@ -94,7 +94,7 @@ describe ('encryption', () => {
     })
       .toThrowError (
         // eslint-disable-next-line max-len
-        'error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt'
+        /bad decrypt/ui
       );
   });
 
diff --git a/test/spec/rsa.js b/test/spec/rsa.js
index 5daf971..d67adfb 100644
--- a/test/spec/rsa.js
+++ b/test/spec/rsa.js
@@ -19,7 +19,7 @@ describe ('rsa', () => {
   it ('should throw on too small key size', async () => {
     await expectAsync (crypto.generate_keypair (16))
       .toBeRejectedWithError (
-        'error:0408F078:rsa routines:pkey_rsa_ctrl:key size too small'
+        /key size too small/ui
       );
   });
 
diff --git a/test/spec/signatures.js b/test/spec/signatures.js
index 81e36e2..65dbf6f 100644
--- a/test/spec/signatures.js
+++ b/test/spec/signatures.js
@@ -18,26 +18,28 @@ describe ('signatures', () => {
       .uninstall ();
   });
 
-  it ('sign_object', () => {
+  it ('sign_object', async () => {
     const obj = { foo: 'bar' };
-    expect (() => {
-      const str = crypto.sign_object (obj, 'baz');
+    await expectAsync ((async () => {
+      const str = await crypto.sign_object (obj, 'baz');
       expect (typeof str)
         .toEqual ('string');
-    }).not.toThrow ();
+    }) ())
+      .toBeResolved ();
   });
 
   it ('sign_object with rsa key', async () => {
     const obj = { foo: 'bar' };
     const k = await rsa.generate_keypair ();
-    expect (() => {
-      const str = crypto.sign_object (obj, k.private_key);
+    await expectAsync ((async () => {
+      const str = await crypto.sign_object (obj, k.private_key);
       expect (typeof str)
         .toEqual ('string');
-    }).not.toThrow ();
+    }) ())
+      .toBeResolved ();
   });
 
-  it ('verify_signature with rsa key', () => {
+  it ('verify_signature with rsa key', async () => {
     const obj = { foo: 'bar' };
     const str = 'U1GcsN3yZzSKxPH8jhCGTKiswfazB9rMfUtE5351LT11t6EmS7xfPjnt'
     + '.5ytniC6q2ovoF7ZqbD8qk9r2kjjAcA9EYhLwC3wwJKPPsKdHSTFd7d9TzBP1skQ98X'
@@ -54,12 +56,12 @@ describe ('signatures', () => {
     + 'dUmjCLWrOzx8SqdqJYmQJX+6GNswnvVF30bkW+/MJZF/P2jLFtSa24Monh7axIqx\n'
     + '8HG0xDw1Z98WV9oQh/vDP/KAs1cPp0AJlwIDAQAB\n'
     + '-----END RSA PUBLIC KEY-----\n';
-    const ver = crypto.verify_signature (str, key);
+    const ver = await crypto.verify_signature (str, key);
     expect (ver)
       .toEqual (obj);
   });
 
-  it ('verify_signature reject with rsa key', () => {
+  it ('verify_signature reject with rsa key', async () => {
     const str = 'U1GcsN3yZzSKxPH8jhCGTKiswfazB9rMfUtE5351LT11t6EmS7xfPjnt'
     + '.5ytniC6q2ovoF7ZqbD8qk9r2kjjAcA9EYhLwC3wwJKPPsKdHSTFd7d9TzBP1skQ98X'
     + 'LjRUkc2M8M84LmWLg76EvcY2pw6HwsFvCUoZYcKAJp3vkp9MQVrVYdHKMPkBjQKyy2V'
@@ -75,179 +77,185 @@ describe ('signatures', () => {
     + 'dUmjCLWrOzx8SqdqJYmQJX+6GNswnvVF30bkW+/MJZF/P2jLFtSa24Monh7axIqx\n'
     + '8HG0xDw1Z98WV9oQh/vDP/KAs1cPp0AJlwIDAQAB\n'
     + '-----END RSA PUBLIC KEY-----\n';
-    const ver = crypto.verify_signature (str, key);
+    const ver = await crypto.verify_signature (str, key);
     expect (ver)
       .toBeNull ();
   });
 
-  it ('should sign object with key info', () => {
+  it ('should sign object with key info', async () => {
     const obj = { foo: 'bar' };
-    expect (() => {
+    await expectAsync ((async () => {
       const str = crypto.sign_object (obj, 'baz', 'baz');
-      const res = crypto.get_signature_info (str);
+      const res = await crypto.get_signature_info (str);
       expect (res.key_info)
         .toEqual ('baz');
-    }).not.toThrow ();
+    }) ())
+      .toBeResolved ();
   });
 
-  it ('should sign object with custom properties', () => {
+  it ('should sign object with custom properties', async () => {
     const obj = { foo: 'bar' };
-    expect (() => {
+    await expectAsync ((async () => {
       const str = crypto.sign_object (obj, 'baz', { bar: 'baz' });
-      const res = crypto.get_signature_info (str);
+      const res = await crypto.get_signature_info (str);
       expect (res.bar)
         .toEqual ('baz');
-    }).not.toThrow ();
+    }) ())
+      .toBeResolved ();
   });
 
-  it ('should sign object with custom override properties', () => {
+  it ('should sign object with custom override properties', async () => {
     const obj = { foo: 'bar' };
-    expect (() => {
+    await expectAsync ((async () => {
       const str = crypto.sign_object (obj, 'baz', { iat: 'baz' });
-      const res = crypto.get_signature_info (str);
+      const res = await crypto.get_signature_info (str);
       expect (res.iat)
         .toEqual ('baz');
-    }).not.toThrow ();
+    }) ())
+      .toBeResolved ();
   });
 
-  it ('decode_signed', () => {
+  it ('decode_signed', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz');
-    const dec = crypto.decode_signed (str);
+    const dec = await crypto.decode_signed (str);
     expect (obj)
       .toEqual (dec);
   });
 
-  it ('verify_signature', () => {
+  it ('verify_signature', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz');
-    const dec = crypto.verify_signature (str, 'baz');
+    const dec = await crypto.verify_signature (str, 'baz');
     expect (obj)
       .toEqual (dec);
   });
 
-  it ('should verify and return all info', () => {
+  it ('should verify and return all info', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz', { iat: 'baz' });
-    const dec = crypto.verify_signature_get_info (str, 'baz');
+    const dec = await crypto.verify_signature_get_info (str, 'baz');
     expect (dec.obj)
       .toEqual (obj);
     expect (dec.iat)
       .toEqual ('baz');
   });
 
-  it ('should verify signature using function retrieved key', () => {
+  it ('should verify signature using function retrieved key', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz');
-    const dec = crypto.verify_signature (str, () => 'baz');
+    const dec = await crypto.verify_signature (str, () => 'baz');
     expect (obj)
       .toEqual (dec);
   });
 
-  it ('should verify signature using function retrieved timeout 0', () => {
-    const obj = { foo: 'bar' };
-    const str = crypto.sign_object (obj, 'baz');
-    const dec = crypto.verify_signature (str, 'baz', () => 0);
-    expect (obj)
-      .toEqual (dec);
-  });
+  it (
+    'should verify signature using function retrieved timeout 0',
+    async () => {
+      const obj = { foo: 'bar' };
+      const str = crypto.sign_object (obj, 'baz');
+      const dec = await crypto.verify_signature (str, 'baz', () => 0);
+      expect (obj)
+        .toEqual (dec);
+    }
+  );
 
-  it ('should reject tampered signatures', () => {
+  it ('should reject tampered signatures', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz');
-    const dec = crypto.verify_signature (str, 'foo');
+    const dec = await crypto.verify_signature (str, 'foo');
     expect (dec)
       .toEqual (null);
   });
 
-  it ('should return null on invalid input', () => {
-    const ver = crypto.verify_signature (null, 'foo');
+  it ('should return null on invalid input', async () => {
+    const ver = await crypto.verify_signature (null, 'foo');
     expect (ver)
       .toEqual (null);
-    const dec = crypto.decode_signed (null, 'foo');
+    const dec = await crypto.decode_signed (null);
     expect (dec)
       .toEqual (null);
   });
 
-  it ('should not fail verification if timeout unspecified', () => {
+  it ('should not fail verification if timeout unspecified', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz');
 
     jasmine.clock ()
       .tick (36e5);
 
-    const dec = crypto.verify_signature (str, 'baz');
+    const dec = await crypto.verify_signature (str, 'baz');
     expect (obj)
       .toEqual (dec);
   });
 
-  it ('should reject old signatures', () => {
+  it ('should reject old signatures', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz');
 
     jasmine.clock ()
       .tick (50);
 
-    const dec = crypto.verify_signature (str, 'baz', 1);
+    const dec = await crypto.verify_signature (str, 'baz', 1);
     expect (dec)
       .toEqual (null);
   });
 
-  it ('should not reject valid signatures', () => {
+  it ('should not reject valid signatures', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz');
 
     jasmine.clock ()
       .tick (50);
 
-    const dec = crypto.verify_signature (str, 'baz', 100);
+    const dec = await crypto.verify_signature (str, 'baz', 100);
     expect (obj)
       .toEqual (dec);
   });
 
-  it ('should verify signature using function retrieved timeout', () => {
+  it ('should verify signature using function retrieved timeout', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz', { to: 100 });
 
     jasmine.clock ()
       .tick (50);
 
-    const dec = crypto.verify_signature (str, 'baz', (info) => info.to);
+    const dec = await crypto.verify_signature (str, 'baz', (info) => info.to);
     expect (obj)
       .toEqual (dec);
   });
 
-  it ('verify_signature on almost timed out packet', () => {
+  it ('verify_signature on almost timed out packet', async () => {
     const obj = { foo: 'bar' };
     const str = crypto.sign_object (obj, 'baz');
 
     jasmine.clock ()
       .tick (10);
-    const dec = crypto.verify_signature (str, 'baz', 10);
+    const dec = await crypto.verify_signature (str, 'baz', 10);
     expect (obj)
       .toEqual (dec);
   });
 
-  it ('should decode problematic token', () => {
+  it ('should decode problematic token', async () => {
     // eslint-disable-next-line max-len
     const str = 'wEJbzvUywiaiGWZUG6CtCXNkNmRGyVoi9icytpTe4gZhsb8Gk.5PZbhGL525mdV7EmYomTwUei6qULpLaZwSXy92eaUDNgbyXPHsr9dfUCeEBpTqmzuq3VtmmV43epUyWRoHocAsV3.2';
-    const obj = crypto.decode_signed (str);
+    const obj = await crypto.decode_signed (str);
     expect (obj)
       .toEqual ({ id: 1 });
   });
 
-  it ('should automatically reencode b64 tokens', () => {
+  it ('should automatically reencode b64 tokens', async () => {
     // eslint-disable-next-line max-len
     const str = 'eyJpYXQiOjE1ODE0NDAwMTIyODgsIm9iaiI6eyJpZCI6MX19.24ZOsWrnfkNe%2FbM0r7DaVJMqE2bfn2aAM%2BZSzWeSf31OCTlXXNWD34RBL2X5v3UliYQ4IIsLNBFbaW9texPHug%3D%3D';
-    const obj = crypto.decode_signed (str);
+    const obj = await crypto.decode_signed (str);
     expect (obj)
       .toEqual ({ id: 1 });
   });
 
-  it ('verify_signature on b64 string', () => {
+  it ('verify_signature on b64 string', async () => {
     // eslint-disable-next-line max-len
     const str = 'eyJpYXQiOjE2MDkzNDQ4MDMyMjcsIm9iaiI6eyJpZCI6MX19.N762xuMaNbT%2Fqb0uTKST68BZgSnmNxXaHl4GY7iAKqaDDEwZn3biYfg5DgJ45QgPZrndchczDjUqLkyXoqw4KQ%3D%3D';
-    const obj = crypto.verify_signature (str, 'baz');
+    const obj = await crypto.verify_signature (str, 'baz');
     expect (obj)
       .toEqual ({ id: 1 });
   });