How does sequence independent single primer amplification work?
This process is called sequence-independent single primer amplification (or in short SISPA). Its used to amplify unknown sequences for amplification, for example in unknown viruses.
The primers used for this process contain random sequences which should bind to the DNA to be amplified and also known sequences, which can be used a adapters. In the first rounds of PCR only the random primers give rise to specific products, which are amplified exponentially in the later rounds of PCR since the primers fit perfectly then. This is described in detail in this publication:"Random priming PCR strategy to amplify and clone trace amounts of DNA"
Another interesting paper describing the method is:"Sequence-independent, single-primer amplification (SISPA) of complex DNA populations."