A security token is a portable device that authenticates a person's identity electronically by storing some sort of personal information. The owner plugs the security token into a system to grant access to a network service. Security Token Services (STS) issue security tokens that authenticate the person's identity.
Security tokens are cryptographic tokens that pay dividends, share profits, pay interest or invest in other tokens or assets to generate profits for the token holders. This takes care of the liquidity issues.