Android AES/ECB/PKCS7PADDING generate key bouncy castle

Question

I want to generate Random key using AES/ECB/PKCS7PADDING but java does not support PKCS7 padding and in my algo I have to use the same padding, bouncy castle does support PKCS7PADDING but I am unable to understand how to generate key using that

My code :

Security.addProvider(new BouncyCastleProvider());


private byte[] generateSessionKey() throws NoSuchAlgorithmException, NoSuchProviderException {
        KeyGenerator kgen = KeyGenerator.getInstance("AES/ECB/PKCS7PADDING", "BC");
        kgen.init(SYMMETRIC_KEY_SIZE);
        SecretKey key = kgen.generateKey();
        return key.getEncoded();
}

I am receiving error of no such algorithm

Why would you use ECB anyway? http://crypto.stackexchange.com/questions/20941/why-shouldnt-i-use-ecb-encryption?noredirect=1&lq=1 — Michael, Dec 07 '16 at 15:46

score 1 · Accepted Answer · edited May 23 '17 at 11:54

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Key generation for AES does not have to do anything with padding. Padding is required for some modes of operation such as ECB and CBC. But the key itself doesn't rely on the mode or the padding. So you should just use:

KeyGenerator kgen = KeyGenerator.getInstance("AES", "BC");

which will undoubtedly work.

Do not use PKCS#7 padding, substitute "PKCS5Padding" for "PKCS7Padding".

Please take a look here to understand the difference between the padding mechanisms and here for the difference in Java.

I guess Android is using a stripped down Bouncy Castle provider (it was one of the reasons that SpongyCastle was lounged), which would explain the differences between Android and the Java SE provider.

edited May 23 '17 at 11:54

Community

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answered Dec 07 '16 at 16:31

Maarten Bodewes

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same problem KeyGenerator AES/ECB/PKCS5Padding implementation not found, i will try SpongyCastle – GaneshP Dec 07 '16 at 16:39
@GaneshP: You're not paying attention to what he wrote. – President James K. Polk Dec 08 '16 at 22:05
@JamesKPolk I think that was an old comment, the accept of the answer is still there. I changed my answer once to include the KeyGenerator comment. – Maarten Bodewes Dec 08 '16 at 22:10
I was worried he was focusing solely on the second half of your answer. – President James K. Polk Dec 09 '16 at 00:44

Android AES/ECB/PKCS7PADDING generate key bouncy castle

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