"Dowry" e "counter assurance" estão corretíssimos, conforme o "Elsevier's Dictionary of Insurance and Risk Prevention", de J. L. de Lucca. Alguns exemplos e referências de counter assurance:

[PDF]Ethical Aspects of Information Assurance Education
... We introduce the term counter-assurance to describe methods and techniques used to defeat or subvert the protective and defensive measures that are put in ...
www.itoc.usma.edu/Documents/Workshop2001/ paperW1C2(22).pdf

Chapter XVI. Of Persons, Authors, and Things Personated. Hobbes, ...
... such authority be not made manifest unto him upon demand, is no longer obliged, for the covenant made with the author is not valid without his counter-assurance ...
www.bartleby.com/34/5/16.html

SparkNotes: Complete Text of Leviathan
... Authority be not made manifest unto him upon demand, is no longer obliged: For the Covenant made with the Author, is not valid, without his Counter-assurance. ...
pd.sparknotes.com/philosophy/leviathan/section18.html

Certainly an Heirloom
... from your word?" After this, Lord Fawn made some attempt at a stipulation that this assurance to Lizzie was to be founded on the counter-assurance given to him ...
www.princeton.edu/~batke/trollope/eustace/eust_16.html

Behind the myth of Jesus of Nazareth - www.ezboard.com
... Strobel occasionally introduces an opposing viewpoint in the course of seeking a counter-assurance, but such views are always presented so as to set them up ...
pub23.ezboard.com/ fmessageboard91119frm0.showMessage?topicID=359.topic