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--></style></head><body bgcolor=white lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt'>RSA-OAEP supports different hash functions and MGF. SHA-1 is the default.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'>OpenSSL implementation of OAEP wrongly refuses to set the hash algorithm, preventing one from using SHA-2 family:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>$ openssl version<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>OpenSSL 1.0.2l 25 May 2017<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>$ openssl pkeyutl -encrypt -in t1264.dat -out t1264.dat.enc2.oaep -keyform DER -pubin -inkey rsa3072pub.der -pkeyopt rsa_padding_mode:oaep<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>$ openssl pkeyutl -encrypt -in t1264.dat -out t1264.dat.enc2.oaep -keyform DER -pubin -inkey rsa3072pub.der -pkeyopt rsa_padding_mode:oaep -pkeyopt digest:sha256<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>parameter setting error<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>140736155067400:error:06089094:digital envelope routines:EVP_PKEY_CTX_ctrl:invalid operation:pmeth_lib.c:376:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>$ ~/openssl-1.1/bin/openssl version<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>OpenSSL 1.1.0g-dev xx XXX xxxx<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>$ ~/openssl-1.1/bin/openssl pkeyutl -encrypt -in t1264.dat -out t1264.dat.enc2.oaep -keyform DER -pubin -inkey rsa3072pub.der -pkeyopt rsa_padding_mode:oaep<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>$ ~/openssl-1.1/bin/openssl pkeyutl -encrypt -in t1264.dat -out t1264.dat.enc2.oaep -keyform DER -pubin -inkey rsa3072pub.der -pkeyopt rsa_padding_mode:oaep -pkeyopt digest:sha256<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>pkeyutl: Can't set parameter:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>140736155067328:error:06089094:digital envelope routines:EVP_PKEY_CTX_ctrl:invalid operation:crypto/evp/pmeth_lib.c:312:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Courier",serif'>$<o:p></o:p></span></p><div><p class=MsoNormal><span style='font-size:10.5pt;color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.5pt;color:black'>It seems that OpenSSL tries to enforce the incorrect assumption that digest/hash is only applicable to signature padding, but not to encryption padding?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.5pt;color:black'>--<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.5pt;color:black'>Regards,<o:p></o:p></span></p></div><p class=MsoNormal><span style='font-size:10.5pt;color:black'>Uri Blumenthal</span><o:p></o:p></p></div></body></html>