The versatile defender becomes Palace's fifth signing of the summer and links up with Dougie Freedman's squad in time for the trip to Middlesbrough on Saturday.
Blake said: "I'm happy to be here and am looking forward to a new challenge. I know quite a few of the lads from the Welsh squad and when we played against them last year a number of times. I'm looking forward to getting some game time and I'm happy to play whenever the manager selects me."
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