Array based key generation

keygen.m

// Array of ordinals (ASCII character posistions)
NSArray *keyStringCharacterOrdinals = @[@99, @109,.....];
NSMutableString *keyString = [[NSMutableString alloc] initWithCapacity:keyStringCharacterOrdinals.count];
for (NSNumber *characterOrdinal in keyStringCharacterOrdinals) {
  [keyString appendString:[NSString stringWithFormat:@"%c", characterOrdinal.intValue]];
}