Русско-англо-русский юридический словарь

The secrecy of correspondence (German: Briefgeheimnis, French: secret de la correspondance) or literally translated as secrecy of letters, is a fundamental legal principle enshrined in the constitutions of several European countries. It guarantees that the content of sealed letters is never revealed and letters in transit are not opened by government officials or any other third party. (Wikipedia)

"The inviolability of the home was enshrined in law as early as 1604 – in the words of the attorney general: ""The house of everyone is to him as his castle and fortress, as well for his defence against injury and violence, as for his repose.""" (Guardian)