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-rw-r--r--jni/ed25519/open.c48
1 files changed, 48 insertions, 0 deletions
diff --git a/jni/ed25519/open.c b/jni/ed25519/open.c
new file mode 100644
index 00000000..1ec4cd2b
--- /dev/null
+++ b/jni/ed25519/open.c
@@ -0,0 +1,48 @@
+#include <string.h>
+#include "crypto_sign.h"
+#include "crypto_hash_sha512.h"
+#include "crypto_verify_32.h"
+#include "ge.h"
+#include "sc.h"
+
+int crypto_sign_open(
+ unsigned char *m,unsigned long long *mlen,
+ const unsigned char *sm,unsigned long long smlen,
+ const unsigned char *pk
+)
+{
+ unsigned char pkcopy[32];
+ unsigned char rcopy[32];
+ unsigned char scopy[32];
+ unsigned char h[64];
+ unsigned char rcheck[32];
+ ge_p3 A;
+ ge_p2 R;
+
+ if (smlen < 64) goto badsig;
+ if (sm[63] & 224) goto badsig;
+ if (ge_frombytes_negate_vartime(&A,pk) != 0) goto badsig;
+
+ memmove(pkcopy,pk,32);
+ memmove(rcopy,sm,32);
+ memmove(scopy,sm + 32,32);
+
+ memmove(m,sm,smlen);
+ memmove(m + 32,pkcopy,32);
+ crypto_hash_sha512(h,m,smlen);
+ sc_reduce(h);
+
+ ge_double_scalarmult_vartime(&R,h,&A,scopy);
+ ge_tobytes(rcheck,&R);
+ if (crypto_verify_32(rcheck,rcopy) == 0) {
+ memmove(m,m + 64,smlen - 64);
+ memset(m + smlen - 64,0,64);
+ *mlen = smlen - 64;
+ return 0;
+ }
+
+badsig:
+ *mlen = -1;
+ memset(m,0,smlen);
+ return -1;
+}