How do you reset an iPhone App's Keychain?

Question

I would like to know if there is a way to reset my app's Keychain. I am wondering whether anything like [NSUserDefaults resetStandardUserDefaults] exists for keychain. Keychain is not reset even after the app is deleted. So far the only way I know is to reset them one by one from the app.

Answer 1

As all of the answers so far rely on you knowing the identifiers you want to delete, I would like to submit the following solution that deletes ALL existing keys for the app (iOS only)

Objective-C:

-(void)resetKeychain {
    [self deleteAllKeysForSecClass:kSecClassGenericPassword];
    [self deleteAllKeysForSecClass:kSecClassInternetPassword];
    [self deleteAllKeysForSecClass:kSecClassCertificate];
    [self deleteAllKeysForSecClass:kSecClassKey];
    [self deleteAllKeysForSecClass:kSecClassIdentity];
}

-(void)deleteAllKeysForSecClass:(CFTypeRef)secClass {
    NSMutableDictionary* dict = [NSMutableDictionary dictionary];
    [dict setObject:(__bridge id)secClass forKey:(__bridge id)kSecClass];
    OSStatus result = SecItemDelete((__bridge CFDictionaryRef) dict);
    NSAssert(result == noErr || result == errSecItemNotFound, @"Error deleting keychain data (%ld)", result);
}

Swift 2.2:

func resetKeychain() {
    self.deleteAllKeysForSecClass(kSecClassGenericPassword)
    self.deleteAllKeysForSecClass(kSecClassInternetPassword)
    self.deleteAllKeysForSecClass(kSecClassCertificate)
    self.deleteAllKeysForSecClass(kSecClassKey)
    self.deleteAllKeysForSecClass(kSecClassIdentity)
}

func deleteAllKeysForSecClass(secClass: CFTypeRef) {
    let dict: [NSString : AnyObject] = [kSecClass : secClass]
    let result = SecItemDelete(dict)
    assert(result == noErr || result == errSecItemNotFound, "Error deleting keychain data (\(result))")
}

Swift 3:

func resetKeychain() {
    deleteAllKeysForSecClass(kSecClassGenericPassword)
    deleteAllKeysForSecClass(kSecClassInternetPassword)
    deleteAllKeysForSecClass(kSecClassCertificate)
    deleteAllKeysForSecClass(kSecClassKey)
    deleteAllKeysForSecClass(kSecClassIdentity)
}

func deleteAllKeysForSecClass(_ secClass: CFTypeRef) {
    let dict: [NSString : Any] = [kSecClass : secClass]
    let result = SecItemDelete(dict as CFDictionary)
    assert(result == noErr || result == errSecItemNotFound, "Error deleting keychain data (\(result))")
}