It’s a tough job to build Flash for the iPhone and Adobe’s CEO, Shantanu Narayen, acknowledged it. In an interview with Bloomberg at the World Economic Forum in Davos, Switzerland, Mr. Narayer said the complicated two-way process of developing Flash for iPhone remains a tough nut to crack.

The CEO put it nicely, underlining that this is why Apple and Adobe are collaborating, because it is “a hard technical challenge.”

"The ball is in our court. The onus is on us to deliver," the Adobe chief told Bloomberg Television.

Mr. Narayen did not elaborate on the hurdles the two companies are making efforts to jump over, but his words suggested that Apple is involved in the process more than ever. Narayen did say, however, that he was "pleased with progress."

Nevertheless, the real obstacle might be - as Apple CEO Steve Jobs said - the nature of Flash itself. The desktop Flash requires too many resources and a small processor of a smartphone and the device’s low memory wouldn’t cope with the situation. On the other hand, a Flash Lite would most likely be too feature-limited, as Steve Jobs put it. So a Flash version made especially for Apple would be the solution.

Adobe said in September, 2008, that a custom version would be released in a very short period if Apple agreed with it. It is not known what happened - either Apple didn’t like it or Flash didn’t - but the custom Flash version didn’t come.

In the meantime, Apple has been collaborating with browser developers Mozilla and Opera to perform the same functions of Flash, but in an environment with far less resources.