Add crypto_sign_ed25519_sk_to_seed() and crypto_sign_ed25519_sk_to_pk()

src/libsodium/crypto_sign/ed25519/sign_ed25519_api.c

@@ -1,3 +1,6 @@
+
+#include <string.h>
+
 #include "crypto_sign_ed25519.h"
 
 size_t
@@ -19,3 +22,18 @@ size_t
 crypto_sign_ed25519_secretkeybytes(void) {
     return crypto_sign_ed25519_SECRETKEYBYTES;
 }
+
+int
+crypto_sign_ed25519_sk_to_seed(unsigned char *seed, const unsigned char *sk)
+{
+    memmove(seed, sk, crypto_sign_ed25519_SEEDBYTES);
+    return 0;
+}
+
+int
+crypto_sign_ed25519_sk_to_pk(unsigned char *pk, const unsigned char *sk)
+{
+    memmove(pk, sk + crypto_sign_ed25519_SEEDBYTES,
+            crypto_sign_ed25519_PUBLICKEYBYTES);
+    return 0;
+}

src/libsodium/include/sodium/crypto_sign_ed25519.h

@@ -64,6 +64,14 @@ int crypto_sign_ed25519_pk_to_curve25519(unsigned char *curve25519_pk,
 SODIUM_EXPORT
 int crypto_sign_ed25519_sk_to_curve25519(unsigned char *curve25519_sk,
                                          const unsigned char *ed25519_sk);
+
+SODIUM_EXPORT
+int crypto_sign_ed25519_sk_to_seed(unsigned char *seed,
+                                   const unsigned char *sk);
+
+SODIUM_EXPORT
+int crypto_sign_ed25519_sk_to_pk(unsigned char *pk, const unsigned char *sk);
+
 #ifdef __cplusplus
 }
 #endif

test/default/sign.c

@@ -1052,6 +1052,8 @@ static TestData test_data[] = {
 
 int main(void)
 {
+    unsigned char      extracted_seed[crypto_sign_ed25519_SEEDBYTES];
+    unsigned char      extracted_pk[crypto_sign_ed25519_PUBLICKEYBYTES];
     unsigned char      sig[crypto_sign_BYTES];
     unsigned char      sm[1024 + crypto_sign_BYTES];
     unsigned char      m[1024];
@@ -1127,6 +1129,16 @@ int main(void)
         printf("crypto_sign_seed_keypair() failure\n");
         return -1;
     }
+    crypto_sign_ed25519_sk_to_seed(extracted_seed, sk);
+    if (memcmp(extracted_seed, keypair_seed,
+               crypto_sign_ed25519_SEEDBYTES) != 0) {
+        printf("crypto_sign_ed25519_sk_to_seed() failure\n");
+    }
+    crypto_sign_ed25519_sk_to_pk(extracted_pk, sk);
+    if (memcmp(extracted_pk, pk,
+               crypto_sign_ed25519_PUBLICKEYBYTES) != 0) {
+        printf("crypto_sign_ed25519_sk_to_pk() failure\n");
+    }
     sodium_bin2hex(pk_hex, sizeof pk_hex, pk, sizeof pk);
     sodium_bin2hex(sk_hex, sizeof sk_hex, sk, sizeof sk);