diff --git a/xcode/OLMKit/OLMAccount.m b/xcode/OLMKit/OLMAccount.m
index 9e48c2d..55e50a1 100644
--- a/xcode/OLMKit/OLMAccount.m
+++ b/xcode/OLMKit/OLMAccount.m
@@ -21,6 +21,7 @@
 #import "OLMSession.h"
 #import "OLMSession_Private.h"
 #import "OLMUtility.h"
+#import "OLMKit.h"
 
 @import Security;
 
@@ -243,6 +244,13 @@
 
         self = [self initWithSerializedData:pickle key:key error:&error];
     }
+    else if ([version isEqualToString:@"2"]) {
+        NSString *pickle = [decoder decodeObjectOfClass:[NSString class] forKey:@"pickle"];
+        NSData *key = OLMKit.sharedInstance.pickleKeyDelegate.pickleKey;
+        NSParameterAssert(key);
+        
+        self = [self initWithSerializedData:pickle key:key error:&error];
+    }
     
     NSParameterAssert(error == nil);
     NSParameterAssert(self != nil);
@@ -254,14 +262,23 @@
 }
 
 - (void)encodeWithCoder:(NSCoder *)encoder {
-    NSData *key = [OLMUtility randomBytesOfLength:32];
+    NSData *key = OLMKit.sharedInstance.pickleKeyDelegate.pickleKey;
+    if (key)
+    {
+        [encoder encodeObject:@"2" forKey:@"version"];
+    }
+    else
+    {
+        key = [OLMUtility randomBytesOfLength:32];
+        [encoder encodeObject:key forKey:@"key"];
+        [encoder encodeObject:@"1" forKey:@"version"];
+    }
+    
     NSError *error = nil;
     NSString *pickle = [self serializeDataWithKey:key error:&error];
     NSParameterAssert(pickle.length > 0 && error == nil);
     
     [encoder encodeObject:pickle forKey:@"pickle"];
-    [encoder encodeObject:key forKey:@"key"];
-    [encoder encodeObject:@"1" forKey:@"version"];
 }
 
 
diff --git a/xcode/OLMKit/OLMInboundGroupSession.m b/xcode/OLMKit/OLMInboundGroupSession.m
index 9e57741..7e0eace 100644
--- a/xcode/OLMKit/OLMInboundGroupSession.m
+++ b/xcode/OLMKit/OLMInboundGroupSession.m
@@ -19,6 +19,7 @@
 
 #import "OLMUtility.h"
 #include "olm/olm.h"
+#import "OLMKit.h"
 
 @interface OLMInboundGroupSession ()
 {
@@ -277,7 +278,14 @@
 
         self = [self initWithSerializedData:pickle key:key error:&error];
     }
-
+    else if ([version isEqualToString:@"2"]) {
+        NSString *pickle = [decoder decodeObjectOfClass:[NSString class] forKey:@"pickle"];
+        NSData *key = OLMKit.sharedInstance.pickleKeyDelegate.pickleKey;
+        NSParameterAssert(key);
+        
+        self = [self initWithSerializedData:pickle key:key error:&error];
+    }
+    
     NSParameterAssert(error == nil);
     NSParameterAssert(self != nil);
     if (!self) {
@@ -288,14 +296,23 @@
 }
 
 - (void)encodeWithCoder:(NSCoder *)encoder {
-    NSData *key = [OLMUtility randomBytesOfLength:32];
+    NSData *key = OLMKit.sharedInstance.pickleKeyDelegate.pickleKey;
+    if (key)
+    {
+        [encoder encodeObject:@"2" forKey:@"version"];
+    }
+    else
+    {
+        key = [OLMUtility randomBytesOfLength:32];
+        [encoder encodeObject:key forKey:@"key"];
+        [encoder encodeObject:@"1" forKey:@"version"];
+    }
+    
     NSError *error = nil;
     NSString *pickle = [self serializeDataWithKey:key error:&error];
     NSParameterAssert(pickle.length > 0 && error == nil);
-
+    
     [encoder encodeObject:pickle forKey:@"pickle"];
-    [encoder encodeObject:key forKey:@"key"];
-    [encoder encodeObject:@"1" forKey:@"version"];
 }
 
 @end
diff --git a/xcode/OLMKit/OLMKit.h b/xcode/OLMKit/OLMKit.h
index 54496a0..fc660dd 100644
--- a/xcode/OLMKit/OLMKit.h
+++ b/xcode/OLMKit/OLMKit.h
@@ -31,9 +31,31 @@
 #import <OLMKit/OLMPkSigning.h>
 #import <OLMKit/OLMSAS.h>
 
-@interface OLMKit : NSObject
 
-//! Project version string for OLMKit, the same as libolm.
-+ (NSString*)versionString;
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ `OLMKitPickleKeyDelegate` provides the key to use for every pickle operation.
+ */
+@protocol OLMKitPickleKeyDelegate <NSObject>
+
+- (NSData*)pickleKey;
 
 @end
+
+
+@interface OLMKit : NSObject
+
+/// Project version string for OLMKit, the same as libolm.
++ (NSString*)versionString;
+
+/// The optional delegate that provides the pickle key.
+/// If not provided, OLMKit will use default pickle keys.
+@property (nonatomic, weak, nullable) id<OLMKitPickleKeyDelegate> pickleKeyDelegate;
+
+/// The singleton instance.
++ (instancetype)sharedInstance;
+
+@end
+
+NS_ASSUME_NONNULL_END
diff --git a/xcode/OLMKit/OLMKit.m b/xcode/OLMKit/OLMKit.m
index c383650..332f0dd 100644
--- a/xcode/OLMKit/OLMKit.m
+++ b/xcode/OLMKit/OLMKit.m
@@ -30,4 +30,15 @@
     return [NSString stringWithFormat:@"%tu.%tu.%tu", major, minor, patch];
 }
 
++ (instancetype)sharedInstance
+{
+    static OLMKit *sharedInstance = nil;
+    
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        sharedInstance = [[self alloc] init];
+    });
+    return sharedInstance;
+}
+
 @end
diff --git a/xcode/OLMKit/OLMOutboundGroupSession.m b/xcode/OLMKit/OLMOutboundGroupSession.m
index a0a7cc6..3a4ef3d 100644
--- a/xcode/OLMKit/OLMOutboundGroupSession.m
+++ b/xcode/OLMKit/OLMOutboundGroupSession.m
@@ -20,6 +20,8 @@
 #import "OLMUtility.h"
 #include "olm/olm.h"
 
+#import "OLMKit.h"
+
 @interface OLMOutboundGroupSession ()
 {
     OlmOutboundGroupSession *session;
@@ -198,6 +200,14 @@
 
         self = [self initWithSerializedData:pickle key:key error:&error];
     }
+    else if ([version isEqualToString:@"2"]) {
+        NSString *pickle = [decoder decodeObjectOfClass:[NSString class] forKey:@"pickle"];
+        NSData *key = OLMKit.sharedInstance.pickleKeyDelegate.pickleKey;
+        NSParameterAssert(key);
+        
+        self = [self initWithSerializedData:pickle key:key error:&error];
+    }
+        
 
     NSParameterAssert(error == nil);
     NSParameterAssert(self != nil);
@@ -209,14 +219,23 @@
 }
 
 - (void)encodeWithCoder:(NSCoder *)encoder {
-    NSData *key = [OLMUtility randomBytesOfLength:32];
+    NSData *key = OLMKit.sharedInstance.pickleKeyDelegate.pickleKey;
+    if (key)
+    {
+        [encoder encodeObject:@"2" forKey:@"version"];
+    }
+    else
+    {
+        key = [OLMUtility randomBytesOfLength:32];
+        [encoder encodeObject:key forKey:@"key"];
+        [encoder encodeObject:@"1" forKey:@"version"];
+    }
+
     NSError *error = nil;
     NSString *pickle = [self serializeDataWithKey:key error:&error];
     NSParameterAssert(pickle.length > 0 && error == nil);
 
     [encoder encodeObject:pickle forKey:@"pickle"];
-    [encoder encodeObject:key forKey:@"key"];
-    [encoder encodeObject:@"1" forKey:@"version"];
 }
 
 @end
diff --git a/xcode/OLMKit/OLMPkDecryption.m b/xcode/OLMKit/OLMPkDecryption.m
index 4af2c71..cf77375 100644
--- a/xcode/OLMKit/OLMPkDecryption.m
+++ b/xcode/OLMKit/OLMPkDecryption.m
@@ -19,6 +19,7 @@
 #include "olm/olm.h"
 #include "olm/pk.h"
 #include "OLMUtility.h"
+#import "OLMKit.h"
 
 @interface OLMPkDecryption ()
 {
@@ -274,7 +275,14 @@
 
         self = [self initWithSerializedData:pickle key:key error:&error];
     }
-
+    else if ([version isEqualToString:@"2"]) {
+        NSString *pickle = [decoder decodeObjectOfClass:[NSString class] forKey:@"pickle"];
+        NSData *key = OLMKit.sharedInstance.pickleKeyDelegate.pickleKey;
+        NSParameterAssert(key);
+        
+        self = [self initWithSerializedData:pickle key:key error:&error];
+    }
+    
     NSParameterAssert(error == nil);
     NSParameterAssert(self != nil);
     if (!self) {
@@ -285,15 +293,23 @@
 }
 
 - (void)encodeWithCoder:(NSCoder *)encoder {
-    NSData *key = [OLMUtility randomBytesOfLength:32];
-    NSError *error = nil;
+    NSData *key = OLMKit.sharedInstance.pickleKeyDelegate.pickleKey;
+    if (key)
+    {
+        [encoder encodeObject:@"2" forKey:@"version"];
+    }
+    else
+    {
+        key = [OLMUtility randomBytesOfLength:32];
+        [encoder encodeObject:key forKey:@"key"];
+        [encoder encodeObject:@"1" forKey:@"version"];
+    }
     
+    NSError *error = nil;
     NSString *pickle = [self serializeDataWithKey:key error:&error];
     NSParameterAssert(pickle.length > 0 && error == nil);
-
+    
     [encoder encodeObject:pickle forKey:@"pickle"];
-    [encoder encodeObject:key forKey:@"key"];
-    [encoder encodeObject:@"1" forKey:@"version"];
 }
 
 @end