Final answer:
Wallachian princes used wax seals to sign their titles on documents, which served as a secure method of authentication common among the nobility in the medieval era.
Step-by-step explanation:
The Wallachian princes signed their titles in documents using a wax seal. Seals have been used historically in many cultures as a means of authenticating documents. Indeed, seals worked both to secure the contents of a letter or document and to identify the sender. The use of wax seals by nobility and royalty was common across Europe during the medieval period, and this practice extended to the region of Wallachia as well.
Signatures alone could be replicated or forged, whereas a seal, often marked with a unique family crest or emblem, presented a much higher threshold of authenticity. While swords and blood were also symbols of power and personal honor, their uses were different; swords were typically associated with a person's military prowess and valor, and blood might be used symbolically or in oaths, but not commonly for mundane documentation such as seals of letters or edicts.