Her new celebrity status was put firmly beyond doubt when, soon after the win, she was approached by the Pepsi Cola company to promote its product, an offer she and her parents decided to turn down. She also found herself described as having real "girl power" in a substantial write-up which appeared in the Spice Girls' pop magazine.
Soon, a plethora of offers began to roll in, for Sarah and her parents. She describes in her book how she and her father flew to Singapore as guests of its government, so she could deliver a formal lecture. She also met students as part of Singapore's efforts to encourage young people into the sciences.
In Milan, she addressed 200 senior women within the IBM corporation. Sarah had no experience of public speaking and it was completely foreign to her, yet true to her usual approach to a challenge, she not only delivered the lectures, but garnered a standing ovation after her talk in Milan.
Her trip to Stockholm last December to attend the Nobel Prize award-ceremony was part of her prize for a first place, representing Ireland, in the European Contest for Young Scientists last autumn in Thessaloniki, in Greece. Access to this competition in turn had come from her win in Dublin.
Other phone-calls to the Flannery home promised great riches if Sarah was willing to patent and commercialise her discovery of a powerful new method to encrypt computer data. It became a talking point across the Internet, with some congratulating Sarah's and her father's decision not to patent and others describing them as foolish and guilty of squandering a fortune.
She describes in the book one meeting with a US investor who offered to build a company around her. He arrived on a private jet for a meeting lasting several hours before jetting off to Monte Carlo, although nothing further came of the meeting.
A lot of nonsense was written at the time, she said, with claims for the value of her findings going up, auction-like, from thousands to millions and eventually to a ridiculous billions of punts. But she and her father had early on determined to shun patenting, deciding the right thing was to place this research, like any good science, in the public domain.
The whole issue became moot within months, however, as the encryption formula she had developed came under theoretical "attack" by a fellow research-scientist. He identified a flaw in the formula's design, which meant data could not be protected. This in turn led to one of the worst times and one of the best for Sarah since the Young Scientist award.
When the flaw was described to Sarah she, her father and people with whom she had worked at Baltimore Technologies, a company specialising in cryptography, tried desperately to find what is referred to as a "patch", to save the formula. It was both a sad and stressful time, she says, and they worked for weeks, searching for a workable patch: either they would succeed and the formula on which she had invested so much time would survive, or they would fail and the formula would fall. "The horrible thing was we really didn't know for so long."
In the end, no patch could be found and they realised the formula, the Cayley-Purser Algorithm, was vulnerable to attack. This was confirmed before her trip to the EU's young scientist competition in Greece and, choosing to be honest about her science, she included this new information in her project report. She assumed the competition judges would pass over her project because of the formula's fatal flaw: instead, they awarded her one of the three first-place prizes for her efforts, leading her to describe the EU win as one of the "nicest parts of the whole thing".
As to her book, she was approached within 10 days of the Young Scientist award with an offer from Profile Books. "We were very reluctant to take on the project at first," Sarah recalls, both because of the media deluge but also because of the time and effort it would take. Then, once they finally agreed to go ahead with it, they realised a March launch would put them right in the midst of Sarah's preparations for the Leaving Cert. She would have been doubly slow to accept had she realised this, she admits.
And yet she did agree, and she has put as much effort into it as she did into her Esat Young Scientist project and into those first public-speaking engagements. It was all new territory but she shirked neither the opportunity nor the responsibility. It is very much in keeping with this young woman, someone to watch in the coming years.
In Code, A Mathematical Journey by Sarah Flannery with David Flannery is published by Profile Books, at £14.99 in UK. An extract from In Code will appear on Monday's Science Today page. Sarah Flannery will give a public lecture, "Making Maths Fun Through Puzzles", sponsored by Intel, in the RDS on April 17th, at 7 p.m. Further details will be published in The Irish Times.