BCM20737 RSA question

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Anonymous
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I am doing OTA with BCM20737,and do it success with the source code which jamesle1 provided.

But have some worried about the RSA in BCM20737.

RSA means we have one public KEY and have a lot of privite KEY,But when I execused the WsRsaKeyGen.exe,then I have the file rsa.pri and rsa_pub.c.And if execused WsRsaKeyGen.exe again then I have another two different file rsa.pri and rsa_pub.c.How do I use these four file.

If we have a lot of device,which is the only public KEY.

How should I understand the BCM20737 's RSA .

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1 Solution

When you execute "WsRsaKeyGen.exe" once, one set of private and public key is generated. They MUST be used as a single set. Meaning to say, Public_key_A must be used with Private_key_A. In the incident you just described above, you are using Public_key_A with Private_key_B, of which of course will fail.

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MichaelF_56
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Anonymous
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yes I readed the file.The question is if I have only one device it workes.But if I have many devices,if these devices have the same public KEY and privite KEY.

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The whole idea is to re-use the public key (rsa_pub.c) when you developed a new version of your application. Then use your private key (rsa.pri) to sign it to become your new FW release for upgrading. The actual upgrading must involved a connection between your product to a client and so it is quite safe.

For a single product development, you only need to carry out the "WsRsaKeyGen.exe" process once in principal. Place the public key in your secure_ota_FW_upgrade folder and keep the private key together with your "WsRsaSign.exe".

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Anonymous
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Thanks boont. I am not exactly sure,if I re-use the public key(rsa_pub.c),then I must  re-use the privite key(rsa.pri).if so ,I am  confused by RSA's asymmetric encryption.

And I do a test if I re_use the public key(rsa_pub.c),and I use a new privite key.when I am doing OTA uptdata, I get error WS_UPGRADE_STATUS_VERIFICATION_FAILED.

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When you execute "WsRsaKeyGen.exe" once, one set of private and public key is generated. They MUST be used as a single set. Meaning to say, Public_key_A must be used with Private_key_A. In the incident you just described above, you are using Public_key_A with Private_key_B, of which of course will fail.

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Anonymous
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ok, I understand.thanks a lot.

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