The European Convention on Human Rights is based on the idea of civil liberties, 18 articles in total. What philosophy is the foundation for these liberties? Specifically the right to privacy/private life?
Welcomem Himmators. This is an interesting; the answer to it isn't at all obvious. There was some derivation from the 1948 Universal Declaration of Human Rights (https://www.equalityhumanrights.com/en/what-are-human-rights/what-universal-declaration-human-rights). Otherwise the main answer lies in intellectual history - the history of ideas - mainly I think from the 18th century : the American Declaration of Independence (1776) and the French Declaration of the Rights of Man and of the Citizen (1789).
American Declaration of Independence : https://en.wikipedia.org/wiki/United_States_Declaration_of_Independence
French Declaration of the Rights of Man and of the Citizen : https://en.wikipedia.org/wiki/Declaration_of_the_Rights_of_the_Man_and_of_the_Citizen_of_1789
The case for going back this far is that rights-talk receded in the 19th and early 20th centuries, partly because of its revolutionary associations and partly because the major ethical and political theories dominant in the West did not stress rights.
Utilitarianism was not a rights-based morality : it sought to produce the greatest happiness of the greatest number. Jeremy Bentham regarded 'natural rights' as 'nonsense upon stilts' and John Stuart Mill was emphatic in On Liberty (1859) that 'It is proper to state that I forego any advantage which could be derived to my argument from the idea of abstract right, as a thing independent of utility', where it is fair to gloss 'abstract' as 'natural' : www.gutenberg.org/files/34901/34901-h/34901-h.htm. Mill finds a place for rights in chapter 5 of Utilitarianism (1863) in his account of justice - but not for abtract, natural or human rights :http://www.gutenberg.org/files/11224/11224-h/11224-h.htm.
Counterbalancing utilitarianism, the ethical theory of Kant accommodated civil rights but not what we should recognise as natural or human rights. Kantian rational morality had closer affinities with the Natural Law tradition than to that of natural rights.
What gave fresh relevance to the American and French emphasis on natural rights were the severe moral offences that occurred during the Second World War. International law in its then state was inadequate to bring the Nazis and their collaborators to full legal justice, and so natural or as they came increasingly to be called 'human rights' became a legal resource in the Nuremberg Trials.
Once invoked in this way, human rights seemed increasingly a plausible framework within which entire political systems, and in the European case the group of Western European states, should operate.