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The cryptocurrency market came storming back Friday after a holiday slump.

The market capitalization for cryptocurrencies retested old highs, crossing back over $600 billion. The market first hit the milestone on December 18. It bottomed out four days later at $412 billion.

The biggest gains in the market were not among the top known cryptos - such as bitcoin and Ethereum - but smaller so-called alt-coins. Here's the scoreboard for Friday:

Smaller coins, such as Cardano and Stellar, were up more than 20% apiece, according to data provider CoinMarketCap.com.

What's happening: