diff --git a/sys/crypto/rc5.c b/sys/crypto/rc5.c
index 294f3369c6..0463e9c2e5 100644
--- a/sys/crypto/rc5.c
+++ b/sys/crypto/rc5.c
@@ -63,7 +63,8 @@ int rc5_encrypt(cipher_context_t *context, uint8_t *block,
 {
     register uint32_t l;
     register uint32_t r;
-    register uint32_t *s = ((rc5_context_t *) context->context)->skey;
+    rc5_context_t *rc5_context = (rc5_context_t *) context->context;
+    register uint32_t *s = rc5_context->skey;
     uint8_t i, tmp;
     c2l(block, l);
     block += 4;
@@ -95,8 +96,8 @@ int rc5_decrypt(cipher_context_t *context, uint8_t *cipherBlock,
 {
     register uint32_t l;
     register uint32_t r;
-    register uint32_t *s = ((rc5_context_t *) context->context)->skey +
-                           (2 * RC5_ROUNDS) + 1;
+    rc5_context_t *rc5_context = (rc5_context_t *) context->context;
+    register uint32_t *s = rc5_context->skey + (2 * RC5_ROUNDS) + 1;
     uint8_t i, tmp;
 
     c2l(cipherBlock, l);
@@ -131,7 +132,8 @@ int rc5_setup_key(cipher_context_t *context, uint8_t *key, uint8_t keysize)
     uint8_t ii, jj, m;
     int8_t i;
     uint8_t tmp[8];
-    S = ((rc5_context_t *)context->context)->skey;
+    rc5_context_t *rc5_context = (rc5_context_t *) context->context;
+    S = rc5_context->skey;
 
     //dumpBuffer ("RC5M:setupKey K", (uint8_t *)key, 8);
     c2l(key, l);
@@ -154,7 +156,7 @@ int rc5_setup_key(cipher_context_t *context, uint8_t *key, uint8_t keysize)
     //dumpBuffer ("RC5M: setupKey S", (uint8_t *)S, 2 * (RC5_ROUNDS +1) * 4);
     ii = jj = 0;
     A = B = 0;
-    S = ((rc5_context_t *)context->context)->skey;
+    S = rc5_context->skey;
 
     for (i = 3 * (2 * RC5_ROUNDS + 2) - 1; i >= 0; i--) {
         k = (*S + A + B)&RC5_32_MASK;
@@ -168,7 +170,7 @@ int rc5_setup_key(cipher_context_t *context, uint8_t *key, uint8_t keysize)
 
         if (++ii >= 2 * RC5_ROUNDS + 2) {
             ii = 0;
-            S = ((rc5_context_t *)context->context)->skey;
+            S = rc5_context->skey;
         }
 
         jj ^= 4;
diff --git a/sys/crypto/skipjack.c b/sys/crypto/skipjack.c
index 7acc770c41..fea74652d8 100644
--- a/sys/crypto/skipjack.c
+++ b/sys/crypto/skipjack.c
@@ -137,7 +137,8 @@ int skipjack_encrypt(cipher_context_t *context, uint8_t *plainBlock,
 
     // prologue 10 pushs = 20 cycles
     /*register*/ uint8_t counter = 1;
-    /*register*/ uint8_t *skey  = ((skipjack_context_t *)context->context)->skey;
+    skipjack_context_t *skipjack_context = (skipjack_context_t *)context->context;
+    /*register*/ uint8_t *skey  = skipjack_context->skey;
     /*register*/ uint16_t w1, w2, w3, w4, tmp;
     /*register*/ uint8_t bLeft, bRight;
 
@@ -172,7 +173,7 @@ int skipjack_encrypt(cipher_context_t *context, uint8_t *plainBlock,
         RULE_A(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey = ((skipjack_context_t *)context->context)->skey;
+    skey = skipjack_context->skey;
 
     while (counter < 9) { // 3x
         RULE_A(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
@@ -182,13 +183,13 @@ int skipjack_encrypt(cipher_context_t *context, uint8_t *plainBlock,
         RULE_B(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey = ((skipjack_context_t *)context->context)->skey;
+    skey = skipjack_context->skey;
 
     while (counter < 16) { // 5x
         RULE_B(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey = ((skipjack_context_t *)context->context)->skey;
+    skey = skipjack_context->skey;
     // 1x
     RULE_B(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
 
@@ -196,7 +197,7 @@ int skipjack_encrypt(cipher_context_t *context, uint8_t *plainBlock,
         RULE_A(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey = ((skipjack_context_t *)context->context)->skey;
+    skey = skipjack_context->skey;
 
     while (counter < 25) { // 4x
         RULE_A(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
@@ -204,13 +205,13 @@ int skipjack_encrypt(cipher_context_t *context, uint8_t *plainBlock,
 
     // 1x
     RULE_B(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
-    skey = ((skipjack_context_t *)context->context)->skey;
+    skey = skipjack_context->skey;
 
     while (counter < 31) { // 5x
         RULE_B(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey = ((skipjack_context_t *)context->context)->skey;
+    skey = skipjack_context->skey;
 
     while (counter < 33) { // 2x
         RULE_B(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
@@ -233,7 +234,8 @@ int skipjack_decrypt(cipher_context_t *context, uint8_t *cipherBlock,
                      uint8_t *plainBlock)
 {
     /*register*/ uint8_t counter = 32;
-    /*register*/ uint8_t *skey  = ((skipjack_context_t *)context->context)->skey + 4;
+    skipjack_context_t *skipjack_context = (skipjack_context_t *)context->context;
+    /*register*/ uint8_t *skey  = skipjack_context->skey + 4;
     /*register*/ uint16_t w1, w2, w3, w4, tmp;
     /*register*/ uint8_t bLeft, bRight;
 
@@ -267,13 +269,13 @@ int skipjack_decrypt(cipher_context_t *context, uint8_t *cipherBlock,
         RULE_B_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey  = ((skipjack_context_t *)context->context)->skey + 16;
+    skey  = skipjack_context->skey + 16;
 
     while (counter > 25) { //5x
         RULE_B_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey  = ((skipjack_context_t *)context->context)->skey + 16;
+    skey  = skipjack_context->skey + 16;
     //1x
     RULE_B_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
 
@@ -281,7 +283,7 @@ int skipjack_decrypt(cipher_context_t *context, uint8_t *cipherBlock,
         RULE_A_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey  = ((skipjack_context_t *)context->context)->skey + 16;
+    skey  = skipjack_context->skey + 16;
 
     while (counter > 16) { //4x
         RULE_A_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
@@ -289,13 +291,13 @@ int skipjack_decrypt(cipher_context_t *context, uint8_t *cipherBlock,
 
     //1x
     RULE_B_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
-    skey  = ((skipjack_context_t *)context->context)->skey + 16;
+    skey  = skipjack_context->skey + 16;
 
     while (counter > 10) { //5x
         RULE_B_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey  = ((skipjack_context_t *)context->context)->skey + 16;
+    skey  = skipjack_context->skey + 16;
 
     while (counter > 8) { // 2x
         RULE_B_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
@@ -305,7 +307,7 @@ int skipjack_decrypt(cipher_context_t *context, uint8_t *cipherBlock,
         RULE_A_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
     }
 
-    skey  = ((skipjack_context_t *)context->context)->skey + 16;
+    skey  = skipjack_context->skey + 16;
 
     while (counter > 0) { // 5x
         RULE_A_INV(skey, w1, w2, w3, w4, counter, tmp, bLeft, bRight);
@@ -326,7 +328,8 @@ int skipjack_decrypt(cipher_context_t *context, uint8_t *cipherBlock,
 int skipjack_setup_key(cipher_context_t *context, uint8_t *key, uint8_t keysize)
 {
     int i = 0;
-    uint8_t *skey = ((skipjack_context_t *)context->context)->skey;
+    skipjack_context_t *skipjack_context = (skipjack_context_t *)context->context;
+    uint8_t *skey = skipjack_context->skey;
 
     // for keys which are smaller than 160 bits, concatenate until they reach
     // 160 bits in size. Note that key expansion is just concatenation.