Their identities were kept secret.

他们的身份保密。

《牛津词典》

It was ludicrous to suggest that the visit could be kept secret.

认为此次访问可以保密的想法真是荒唐可笑。

《柯林斯英汉双解大词典》

The location of the wreck, which is being kept secret, shows that it did not founder because of navigational error.

沉船的方位仍在保密之中，但它已经表明舰只不是由于航海方面的失误而沉没的。

youdao

Cleveland agreed. But he said the operation would have to be kept secret.

VOA: special.2010.06.17

Hacking believes that there were many gambling theorists who invented probability theory at various times in history but never wrote it down and kept it as a secret.

哈金相信历史上有很多赌博理论家,曾多次构想了概率论,但从来没有记录下来,并且恐为人知

耶鲁公开课 - 金融市场课程节选

The news of this discovery could not be kept secret very long.

VOA: special.2009.02.04

It is a well-kept secret on Wall Street which outside firms have access to these invisible markets.

FORBES: Watch Out For The Quants

He believed their explanation that for political reasons the relationship had to be kept secret.

FORBES: Dr. King and the Klansman -- Love in a Time of Vitriol

However the precise location is being kept secret in case of an invasion of curious visitors.

BBC: News | Sci/Tech | New dinosaur discovered in England