Description |
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A weakness has been found in the generation of ephemeral keys in the ElGamal encryption of libgcrypt when the recipient's key is not generated using the same or a compatible implementation. |
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Libgcrypt before 1.9.3 mishandles ElGamal encryption because it lacks exponent blinding to address a side-channel attack against mpi_powm, and the window size is not chosen appropriately. (There is also an interoperability problem because the selection of the k integer value does not properly consider the differences between basic ElGamal encryption and generalized ElGamal encryption.) This, for example, affects use of ElGamal in OpenPGP. |
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