diff --git a/core/modules/deserializers.js b/core/modules/deserializers.js
index 6c6119e25..89584c9ce 100644
--- a/core/modules/deserializers.js
+++ b/core/modules/deserializers.js
@@ -100,7 +100,7 @@ exports["text/html"] = function(text,fields) {
 	var storeAreaMarkerRegExp = /<div id=["']?storeArea['"]?( style=["']?display:none;["']?)?>/gi,
 		match = storeAreaMarkerRegExp.exec(text);
 	if(match) {
-		// If so, it's either a classic TiddlyWiki file or a TW5 file
+		// If so, it's either a classic TiddlyWiki file or an unencrypted TW5 file
 		// First read the normal tiddlers
 		var results = deserializeTiddlyWikiFile(text,storeAreaMarkerRegExp.lastIndex,!!match[1],fields);
 		// Then any system tiddlers
@@ -111,8 +111,15 @@ exports["text/html"] = function(text,fields) {
 		}
 		return results
 	} else {
-		// It's not a TiddlyWiki so we'll return the entire HTML file as a tiddler
-		return deserializeHtmlFile(text,fields);
+		// Check whether we've got an encrypted file
+		var encryptedStoreArea = $tw.utils.extractEncryptedStoreArea(text);
+		if(encryptedStoreArea) {
+			// If so, attempt to decrypt it using the current password
+			return $tw.utils.decryptStoreArea(encryptedStoreArea);
+		} else {
+			// It's not a TiddlyWiki so we'll return the entire HTML file as a tiddler
+			return deserializeHtmlFile(text,fields);
+		}
 	}
 };
 
diff --git a/core/modules/utils/crypto.js b/core/modules/utils/crypto.js
new file mode 100644
index 000000000..abeee27ca
--- /dev/null
+++ b/core/modules/utils/crypto.js
@@ -0,0 +1,80 @@
+/*\
+title: $:/core/modules/utils/crypto.js
+type: application/javascript
+module-type: utils
+
+Utility functions related to crypto.
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+/*
+Look for an encrypted store area in the text of a TiddlyWiki file
+*/
+exports.extractEncryptedStoreArea = function(text) {
+	var encryptedStoreAreaStartMarker = "<pre id=\"encryptedStoreArea\" type=\"text/plain\" style=\"display:none;\">",
+		encryptedStoreAreaStart = text.indexOf(encryptedStoreAreaStartMarker);
+	if(encryptedStoreAreaStart !== -1) {
+		var encryptedStoreAreaEnd = text.indexOf("</pre>",encryptedStoreAreaStart);
+		if(encryptedStoreAreaEnd !== -1) {
+			return $tw.utils.htmlDecode(text.substring(encryptedStoreAreaStart + encryptedStoreAreaStartMarker.length,encryptedStoreAreaEnd-1));
+		}
+	}
+	return null;
+};
+
+/*
+Attempt to extract the tiddlers from an encrypted store area using the current password
+*/
+exports.decryptStoreArea = function(encryptedStoreArea) {
+	var decryptedText = $tw.crypto.decrypt(encryptedStoreArea);
+	if(decryptedText) {
+		var json = JSON.parse(decryptedText),
+			tiddlers = [];
+		for(var title in json) {
+			tiddlers.push(json[title]);
+		}
+		return tiddlers;
+	} else {
+		return null;
+	}
+};
+
+exports.decryptStoreAreaInteractive = function(encryptedStoreArea,callback) {
+	// Try to decrypt with the current password
+	var tiddlers = $tw.utils.decryptStoreArea(encryptedStoreArea);
+	if(tiddlers) {
+		callback(tiddlers);
+	} else {
+		// Prompt for a new password and keep trying
+		$tw.passwordPrompt.createPrompt({
+			serviceName: "Enter a password to decrypt the imported TiddlyWiki",
+			noUserName: true,
+			canCancel: true,
+			submitText: "Decrypt",
+			callback: function(data) {
+				// Exit if the user cancelled
+				if(!data) {
+					return false;
+				}
+				// Attempt to decrypt the tiddlers
+				$tw.crypto.setPassword(data.password);
+				var tiddlers = $tw.utils.decryptStoreArea(encryptedStoreArea);
+				if(tiddlers) {
+					callback(tiddlers);
+					// Exit and remove the password prompt
+					return true;
+				} else {
+					// We didn't decrypt everything, so continue to prompt for password
+					return false;
+				}
+			}
+		});
+	}
+};
+
+})();
diff --git a/core/modules/wiki.js b/core/modules/wiki.js
index 866b4dbda..5c21f01d9 100755
--- a/core/modules/wiki.js
+++ b/core/modules/wiki.js
@@ -1083,56 +1083,14 @@ exports.readFile = function(file,callback) {
 			}
 		} else {
 			// Check whether this is an encrypted TiddlyWiki file
-			var encryptedStoreAreaStartMarker = "<pre id=\"encryptedStoreArea\" type=\"text/plain\" style=\"display:none;\">",
-				encryptedStoreAreaStart = text.indexOf(encryptedStoreAreaStartMarker),
-				encryptedStoreAreaEnd = encryptedStoreAreaStart !== -1 ? text.indexOf("</pre>",encryptedStoreAreaStart) : -1;
-			if(encryptedStoreAreaStart !== -1 && encryptedStoreAreaEnd !== -1) {
-				var encryptedJson = $tw.utils.htmlDecode(text.substring(encryptedStoreAreaStart + encryptedStoreAreaStartMarker.length,encryptedStoreAreaEnd-1)),
-					attemptDecryption = function() {
-						var decryptedText = $tw.crypto.decrypt(encryptedJson);
-						if(decryptedText) {
-							var json = JSON.parse(decryptedText),
-								tiddlers = [];
-							for(var title in json) {
-								tiddlers.push(json[title]);
-							}
-							return tiddlers;
-						} else {
-							return null;
-						}
-					};
-				// Try to decrypt with the current password
-				var tiddlers = attemptDecryption();
-				if(tiddlers) {
+			var encryptedJson = $tw.utils.extractEncryptedStoreArea(text);
+			if(encryptedJson) {
+				// If so, attempt to decrypt it with the current password
+				$tw.utils.decryptStoreAreaInteractive(encryptedJson,function(tiddlers) {
 					callback(tiddlers);
-				} else {
-					// Prompt for a new password and keep trying
-					$tw.passwordPrompt.createPrompt({
-						serviceName: "Enter a password to decrypt the imported TiddlyWiki",
-						noUserName: true,
-						canCancel: true,
-						submitText: "Decrypt",
-						callback: function(data) {
-							// Exit if the user cancelled
-							if(!data) {
-								return false;
-							}
-							// Attempt to decrypt the tiddlers
-							$tw.crypto.setPassword(data.password);
-							var tiddlers = attemptDecryption();
-							if(tiddlers) {
-								callback(tiddlers);
-								// Exit and remove the password prompt
-								return true;
-							} else {
-								// We didn't decrypt everything, so continue to prompt for password
-								return false;
-							}
-						}
-					});
-				}
+				});
 			} else {
-				// Try to deserialise any tiddlers in the file
+				// Otherwise, just try to deserialise any tiddlers in the file
 				callback(self.deserializeTiddlers(type,text,tiddlerFields));
 			}
 		}