In Genesis 15:1, the word of the LORD came to Abram saying,
אָנֹכִי מָגֵן לָךְ :
anochi magen lach : I [am a] shield to you.
[This is a photo of me and my brother, Doug, overlooking the ruins of Shilo - where the Tabernacle stood at the time Hannah prayed there for a son - in a Palestinian part of the Holy Land.]
It is believed that the Biblical kings had heraldic symbols to identify them to their troops and to their enemies. The most well-known of these symbols is the Star of David, or the magen david, a symbol still used today on the national flag of Israel.
This calligraphic drawing of the magen (or shield) of David set inside an eight-pointed star is from the Leningrad Codex, the oldest complete manuscript of the Hebrew Bible in Hebrew, using the masoretic text and Tiberian vocalization. It is internally dated AD 1008. In modern times, the Leningrad Codex is most important as the Hebrew text reproduced in Biblia Hebraica (1937) and Biblia Hebraica Stuttgartensia (1977). This is the version of the MT (masoretic text) used by most scholars today.
Here you see the eight-pointed star on the altarcloth between Abel and Melchizedek. Note the hand of God coming through the veil above them.
Many LDS scholars, including Hugh Nibley, believe this symbol to be the magen Melchizedek or call it the seal of Melchizedek. Recently, it has been used in the architecture of and symbolism on several LDS temples. Bryce Haymond has written about the San Diego temple in a four-part series on his blog, Temple Study. Tim Barker has an interesting post on his blog, LDS-Study. A dissenting opinion is well-presented by Alonzo Gaskill here.