The deal was announced Friday as players reported for the start of training camp.
Boston played in all 16 games, 15 as a starter, with the Los Angeles Chargers last season, when he set career highs with 79 tackles, 61 solo, five interceptions and nine passes defensed.
Boston, entering his fifth NFL season, is very familiar with new Cardinals head coach Steve Wilks. A fourth-round selection in the 2014 draft out of North Carolina, Boston played his first three seasons with Carolina, where Wilks was the defensive backs coach.
Arizona released African-born defensive end Moubarak Djeri, who is trying to make the NFL after playing in the German Football League.
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