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We divide a private key into multiple parts (by splitting key string) into N parts and distribute it to different five people. At the time of decryption we collect all keys integrate it (by concatenation) and decrypt it. Is this scheme secure?

Or is it a better idea to split key in to parts using Shamir's Secret Sharing? Which has better security ?

Maarten Bodewes
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Vishvajeet Ramanuj
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    No, it is less secure because by splitting / concatenating you are - by definition - leaking part of the key in plaintext. Private keys are not shared, I'd rather encrypt (wrap) the private key with a symmetric key and share *that*. – Maarten Bodewes Jan 06 '20 at 17:50
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    I'm voting to close this question as off-topic because this is not about programming, and the algorithm is not well researched and not very well described, so it won't be acceptable at [the crypto site](https://crypto.stackexchange.com) – Maarten Bodewes Jan 06 '20 at 17:51
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    What if one of the people loses their part of the key, in a fire say? Better to have multiple places to store each part of the key. Maarten is correct as well. Don't store the key itself (or part of it). Store something else from which the key can be regenerated. – rossum Jan 06 '20 at 19:52
  • Okay. I am curious which is the place for asking question like this ? as @Maarten suggested it is not related to programming and off the topic I got the point Maarten private key should not be shared. what I am trying to do is allowing decryption by not single person but group of more then 2 people. That's why I am dividing key. So It reveal part of key but Is it possible to get other part of private key from one part ? and what about securing it with Shamir's encryption ? – Vishvajeet Ramanuj Jan 10 '20 at 06:42
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    you could post the question to [Cryptography SO](https://crypto.stackexchange.com/), but IMHO this level of questions is better here. As a simple answer, follow the first Maarten's comment. You can wrap (encrypt) the private key using a random symmetric key and use Shamir's sharing to share that. Or check https://stackoverflow.com/questions/59610385/encryption-with-single-key-and-decryption-with-multiple-keys/59611559#59611559 – gusto2 Jan 15 '20 at 07:58

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