The kidnapped man was released during a police operation in Essonne south of Paris late on Saturday, after being abducted on Thursday, according to the country's prosecutor's office.
A police source tells AFP that four men in ski masks snatched the man from a delivery van right in front of witnesses' eyes.
"The victim seems to be the father of a man who has made a fortune on cryptocurrencies. The crime involves demands for ransom," writes the prosecutor in a statement.
According to the newspaper Le Parisien, the perpetrators demanded five to seven million euros, but no payment was made.
During the release, the man had, according to a source, had a finger cut off, and the police feared further mutilation if they did not hurry to release him.
The kidnapping follows a similar incident in January, also in Essonne, when the CEO of a cryptocurrency firm was abducted and found a day later with an amputated finger. Earlier the same month, another man – according to media also the father of a cryptocurrency influencer – was found in the trunk of a car in Le Mans.
It is unclear whether there is any connection between the cases.
