How should I respond when a friend asks me about another friend's secret?

Treating people like you want to be treated is important. If your friend wants you to keep their secrets or information, they should understand you doing the same for another friend. Try reminding them of this fact. Be honest about why their request makes you uncomfortable.

It is important for you to keep the secret because it is not yours. Think of it as a belonging; if you borrowed your friend's shoes because they look really nice, and anothet friend saw them and wanted to borrow them, would you give the shoes to them straight away? No, first you would ask your friend if they would like to share their shoes with your other friend. Then, you would act accordingly. Secrets are even more personal than shoes and should be handled carefully. Cheers. :)

When someone shared his secret with you, it means he trusted you and it is your responsibility to not break the trust of your friend. You can politely reject your other friend and not tell the secret and keep the things on one on one. You can do so by making him realize that how will he feel if you share his secrets with someone else. Try to put your other friend in the shoes of your friend so he can understand your situation better.

Tell them that as much as you care about and respect them, you also care about and respect your other friend and their privacy, and it would be betraying that respect and privacy to tell them your friend's secret.

There are so many ways you can respond to this, particularly if you know this is none of his/her business. One way is to simply say you have no information, another is simply to point to that friend that a secret is a secret and you don't want to gossip. Then change the subject as quickly as you can. There are snarky ways to tell someone that s/he is a tad nosy, but the least said the better. Generally, if anyone has entrusted you with a secret (willingly or not), you'll treat it as confidential business unless you do not care about your (good) reputation.

Politely refuse to tell. You've been asked to keep the secret for a reason, and if they find out you told then they could get angry. If your friend keeps asking and won't relent. tell them to ask the other person themselves.

Clearly, your friend has told you to keep it a secret for a reason. Commenting on that secret is a violation of privacy, and because your friend has entrusted you with some private information, it is your obligation to keep it private until otherwise told by your friend.

I would tell them to stop right there, if I ran about and told people me friends secret. it wouldn't be a secret, now would it? It also shows respect, to keep secrets.

You should maintain confidentiality unless there is a risk factor or the friend is in some considerable danger.