Address review comments

Author: tniessen

lib/internal/crypto/random.js

@@ -124,8 +124,9 @@ function randomFill(buf, offset, size, callback) {
 // e.g.: Buffer.from("ff".repeat(6), "hex").readUIntBE(0, 6);
 const RAND_MAX = 0xFFFF_FFFF_FFFF;
 
-// Cache random data to use in randomInt.
-const randomCache = new FastBuffer(3072);
+// Cache random data to use in randomInt. The cache size must be evenly
+// divisible by 6 because each attempt to obtain a random int uses 6 bytes.
+const randomCache = new FastBuffer(6 * 1024);
 let randomCacheOffset = randomCache.length;
 let asyncCacheFillInProgress = false;
 const asyncCachePendingTasks = [];