add more documentation of decryptSessionKeyEcdh

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dangfan 2021-04-21 19:09:35 +08:00
parent 9ea9bd96bb
commit ec5d5e399f
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1 changed files with 4 additions and 1 deletions

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@ -164,7 +164,10 @@ public class PsoDecryptTokenOp {
/* From rfc6637#section-7 :
The input of KDF should be the x portion of the point.
As the result of ECDH can be expressed in two formats: compressed and uncompressed,
we have to deal with each case.
we have to deal with each case:
An uncompressed point is encoded as 04 || x || y, with x and y are of the same size.
However, a valid x may be led with 04, so we have to also check the length of the result.
A compressed point, on the other hand, is encoded as x only. Therefore, we use the value directly.
int xLen, startPos;
if (keyEncryptionKey[0] == 0x04 && keyEncryptionKey.length % 2 == 1) {