Cryptologist needed

A friend has asked me to try and find someone who can solve a difficult problem. They have some data which has been encrypted by some unscrupulous parties. The data is used by an application which runs under MS-DOS. They're willing to pay for someone's time to retrieve the data as it would be useful for actions they have pending. Anyone out there who can help? I could probably do it myself if I knew of any available decryption software which can run under DOS. Thanks for your attention.