I read some article about the definition of cryptocurrency and digital currency. Still I can not understand their differences. Can a digital currency omits cryptography? Does that make sense? Is cryptocurrency related to mathematical aspects to define secure organization for a digital currency?
From wikipedia I see
Cryptocurrency is a kind of digital currency, virtual currency or alternative currency. and
Digital currency (digital money or electronic money or electronic currency) is a type of currency available only in digital form, not in physical (such as banknotes and coins). There is also a figure at https://en.m.wikipedia.org/wiki/Digital_currency which is not meaningful. What is the relation between cryptocurrency and digital currency?