Fix bad iqmp calculation

closes #62

Author: jschlyter

setup.py

@@ -52,7 +52,7 @@
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
     ],
-    install_requires=["cryptography<=3.0", "requests"],
+    install_requires=["cryptography", "requests"],
     tests_require=["pytest"],
     zip_safe=False,
     extras_require={

src/cryptojwt/jwk/rsa.py

@@ -172,10 +172,10 @@ def rsa_construct_private(numbers):
     try:
         cnum["iqmp"] = numbers["di"]
     except KeyError:
-        cnum["iqmp"] = rsa.rsa_crt_iqmp(cnum["p"], cnum["p"])
+        cnum["iqmp"] = rsa.rsa_crt_iqmp(cnum["p"], cnum["q"])
     else:
         if not numbers["di"]:
-            cnum["iqmp"] = rsa.rsa_crt_iqmp(cnum["p"], cnum["p"])
+            cnum["iqmp"] = rsa.rsa_crt_iqmp(cnum["p"], cnum["q"])
 
     rpubn = rsa.RSAPublicNumbers(e=numbers["e"], n=numbers["n"])
     rprivn = rsa.RSAPrivateNumbers(public_numbers=rpubn, **cnum)