Yosef was born on November 15, 1915 in Sofia, Bulgaria, to Shlomo and Blanche, who were well-off. He graduated the French College in Plovdiv with honors, and he completed a law degree in Sofia. His love of Judaism and Zionism was awakened by Zeev Jabotinsky’s 1937 visit to Bulgaria, in which he warned them about the rise of Nazism. Yosef joined Maccabee, then moved on to Beitar, and within a year he was commanding a cell. His activity was educational and ideological. He set up summer camps and worked to inculcate a Zionist consciousness, while recognizing the history of the Jewish people. His activity was cut short by the German invasion of Bulgaria. Yosef tried to make aliyah illegally, but he failed and was taken first to a forced-labor camp (1941), then a concentration camp (1942-1943). The Red Army liberated him (1944), and he was then able to obtain a certificate and made it to the Land of Israeli.
In Israel, he found himself in dire financial straits. Eventually he found work as a laborer and as a diamond polisher. In 1946, he joined Lehi. Because of his education and his multilingualism (mainly his French), he would serve as a translator from time to time when the underground leaders would meet foreigners. He maintained contacts with the foreign press for public relations and recruitment.
In 1948, he was sent to Czechoslovakia and France, to make contact with journalists and intellectuals. He gathered funds, weapons and support for Israel’s fight for independence among the ruling classes.
When Yosef returned, he worked at the Jewish Agency in absorbing those making aliyah from North Africa. He was very much impressed by their proud and nationalist Judaism, its resilience and deep emotional connection to the homeland. When he left the Jewish Agency after two years, he had difficulty finding work due to his underground past. He worked for some time doing road work in the Arava, and in the end, he travelled to study political science and philosophy in the Sorbonne in Paris. To support himself, he worked as a journalist and a translator.
In 1955, he met Yitzhak Shamir in Paris; Shamir was a Mossad agent at the time, and he recruited him as a local operative. Yosef developed connections among the French Jewish intellectuals, who assisted him in various spheres. In light of his success, he was summoned back to Israel, where he received supplemental training and was sent abroad as a Mossad agent.
On January 25,1964, Yosef married his colleague, Ashira Heiman, and they had a daughter.
Yosef developed connections with leaders and personalities from North Africa, and he spent some time there. After a short time back in Israel, he was sent back to Europe, his residence being in Brussels.
On July 24,1969, when he was in the Israeli Embassy, he had a stroke which proved fatal. His body was flown home and buried in Segula Cemetery, Petah Tikva.