diff --git a/src/crypto/public_key/index.js b/src/crypto/public_key/index.js
index ae4aac89..384dff82 100644
--- a/src/crypto/public_key/index.js
+++ b/src/crypto/public_key/index.js
@@ -7,16 +7,18 @@
  */
 
 /** @see module:crypto/public_key/rsa */
-import rsa from './rsa.js';
+import rsa from './rsa';
+import prime from './prime';
 /** @see module:crypto/public_key/elgamal */
-import elgamal from './elgamal.js';
+import elgamal from './elgamal';
 /** @see module:crypto/public_key/elliptic */
 import elliptic from './elliptic';
 /** @see module:crypto/public_key/dsa */
-import dsa from './dsa.js';
+import dsa from './dsa';
 
 export default {
   rsa: rsa,
+  prime: prime,
   elgamal: elgamal,
   elliptic: elliptic,
   dsa: dsa
diff --git a/src/crypto/public_key/prime.js b/src/crypto/public_key/prime.js
index 75cec019..a35743b9 100644
--- a/src/crypto/public_key/prime.js
+++ b/src/crypto/public_key/prime.js
@@ -15,7 +15,7 @@
 // License along with this library; if not, write to the Free Software
 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 
-// Algorithms for probabilistic primality testing
+// Algorithms for probabilistic prime generation
 
 /**
  * @requires bn.js
@@ -26,21 +26,32 @@
 import BN from 'bn.js';
 import random from '../random';
 
-function randomProbablePrime(b) {
-  let n;
-  const min = new BN(1).shln(b-1);
-  do {
-    n = random.getRandomBN(min, min.shln(1));
-    if (n.isEven()) {
-      n.iaddn(1); // force odd
+export default {
+  randomProbablePrime, isProbablePrime, fermat, millerRabin
+};
+
+function randomProbablePrime(bits, e) {
+  const min = new BN(1).shln(bits - 1);
+
+  let n = random.getRandomBN(min, min.shln(1));
+  if (n.isEven()) {
+    n.iaddn(1); // force odd
+  }
+
+  while (!isProbablePrime(n, e)) {
+    n.iaddn(2);
+    // If reached the maximum, go back to the minimum.
+    if (n.bitLength() > bits) {
+      n = n.mod(min.shln(1)).iadd(min);
     }
-  } while (!isProbablePrime(n));
-//    this.dAddOffset(2, 0);
-//    if (this.bitLength() > b)
-//      this.subTo(BigInteger.ONE.shiftLeft(b - 1), this);
+  }
+  return n;
 }
 
-function isProbablePrime(n) {
+function isProbablePrime(n, e) {
+  if (e && !n.subn(1).gcd(e).eqn(1)) {
+    return false;
+  }
   if (!fermat(n)) {
     return false;
   }
@@ -54,9 +65,9 @@ function isProbablePrime(n) {
  * Tests whether n is probably prime or not using Fermat's test with b = 2.
  * Fails if b^(n-1) mod n === 1.
  */
-export function fermat(n, b) {
+function fermat(n, b) {
   b = b || new BN(2);
-  return b.toRed(BN.mont(n)).redPow(n.subn(1)).cmpn(1) === 0;
+  return b.toRed(BN.mont(n)).redPow(n.subn(1)).fromRed().cmpn(1) === 0;
 }
 
 
@@ -93,7 +104,7 @@ export function fermat(n, b) {
  * Tests whether n is probably prime or not using the Miller-Rabin test.
  * See HAC Remark 4.28.
  */
-export function millerRabin(n, k, cb) {
+function millerRabin(n, k, cb) {
   var len = n.bitLength();
   var red = BN.mont(n);
   var rone = new BN(1).toRed(red);
diff --git a/src/crypto/public_key/rsa.js b/src/crypto/public_key/rsa.js
index 2e86b7d5..3792f1ea 100644
--- a/src/crypto/public_key/rsa.js
+++ b/src/crypto/public_key/rsa.js
@@ -29,9 +29,7 @@
 
 
 import BN from 'bn.js';
-import { RSA } from 'asmcrypto.js/src/rsa/exports-keygen';
 import { RSA_RAW } from 'asmcrypto.js/src/rsa/exports-raw';
-import { random as asmcrypto_random } from 'asmcrypto.js/src/random/exports';
 import prime from './prime';
 import random from '../random';
 import config from '../../config';
@@ -40,6 +38,13 @@ import util from '../../util';
 const two = new BN(2);
 const zero = new BN(0);
 
+// TODO use this is ../../encoding/base64.js and ./elliptic/{key,curve}.js
+function b64toBN(base64url) {
+  const base64 = base64url.replace(/\-/g, '+').replace(/_/g, '/');
+  const hex = util.hexstrdump(atob(base64));
+  return new BN(hex, 16);
+}
+
 export default {
   /** Create signature
    * @param m message as BN
@@ -189,25 +194,27 @@ export default {
       return key;
     }
 
-    // TODO use this is ../../encoding/base64.js and ./elliptic/{key,curve}.js
-    function b64toBN(base64url) {
-      const base64 = base64url.replace(/\-/g, '+').replace(/_/g, '/');
-      const hex = util.hexstrdump(atob(base64));
-      return new BN(hex, 16);
-    }
+    while (true) {
+      let p = prime.randomProbablePrime(B - (B >> 1), E);
+      let q = prime.randomProbablePrime(B >> 1, E);
 
-    // asmcrypto fallback
-    await asmcrypto_random.seed(await random.getRandomBytes(1024)); // FIXME how much randomness?
-    key = await RSA.generateKey(B, E.toArrayLike(Uint8Array));
-    return {
-      n: new BN(key[0]),
-      e: new BN(key[1]),
-      d: new BN(key[2]),
-      q: new BN(key[3]),
-      p: new BN(key[4]),
-      // dq: new BN(key[5]),
-      // dp: new BN(key[6]),
-      u: new BN(key[7])
-    };
+      if (p.cmp(q) < 0) {
+        const t = p;
+        p = q;
+        q = t;
+      }
+
+      const phi = p.subn(1).mul(q.subn(1));
+      return {
+        n: p.mul(q),
+        e: E,
+        d: E.invm(phi),
+        q: q,
+        p: p,
+        // dq: d.mod(q.subn(1)),
+        // dp: d.mod(p.subn(1)),
+        u: p.invm(q)
+      };
+    }
   }
 };