diff --git a/MasterPassword/C/mpw-cli.c b/MasterPassword/C/mpw-cli.c
index c7532176..6cce2806 100644
--- a/MasterPassword/C/mpw-cli.c
+++ b/MasterPassword/C/mpw-cli.c
@@ -138,7 +138,7 @@ int main(int argc, char *const argv[]) {
                 }
                 return 1;
             default:
-                abort();
+                ftl("Unexpected option: %c", opt);
         }
     if (optind < argc)
         siteName = argv[optind];
@@ -199,8 +199,8 @@ int main(int argc, char *const argv[]) {
     fprintf( stderr, "%s's password for %s:\n[ %s ]: ", fullName, siteName, Identicon( fullName, masterPassword ) );
 
     // Output the password.
-    uint8_t *masterKey = mpw_masterKeyForUser( fullName, masterPassword );
-    char *sitePassword = mpw_passwordForSite( masterKey, siteName, siteType, siteCounter, siteVariant, siteContextString );
+    const uint8_t *masterKey = mpw_masterKeyForUser( fullName, masterPassword );
+    const char *sitePassword = mpw_passwordForSite( masterKey, siteName, siteType, siteCounter, siteVariant, siteContextString );
     fprintf( stdout, "%s\n", sitePassword );
 
     return 0;
diff --git a/MasterPassword/C/mpw.c b/MasterPassword/C/mpw.c
index e282698c..ec229e7f 100644
--- a/MasterPassword/C/mpw.c
+++ b/MasterPassword/C/mpw.c
@@ -16,115 +16,101 @@
 #define MP_dkLen            64
 #define MP_hash             PearlHashSHA256
 
-void mpw_bufPush(void *buffer, size_t *bufferSize, void *pushBuffer, size_t pushSize) {
+static void mpw_pushBuf(uint8_t **const buffer, size_t *const bufferSize, const void *pushBuffer, const size_t pushSize) {
 
-    void *pushDst = buffer + *bufferSize;
     *bufferSize += pushSize;
-    realloc( buffer, *bufferSize );
+    *buffer = realloc( *buffer, *bufferSize );
+    uint8_t *pushDst = *buffer + *bufferSize - pushSize;
     memcpy( pushDst, pushBuffer, pushSize );
 }
 
-uint8_t *mpw_masterKeyForUser(const char *fullName, const char *masterPassword) {
+static void mpw_pushString(uint8_t **buffer, size_t *const bufferSize, const char *pushString) {
+
+    mpw_pushBuf( buffer, bufferSize, pushString, strlen( pushString ) );
+}
+
+static void mpw_pushInt(uint8_t **const buffer, size_t *const bufferSize, const uint32_t pushInt) {
+
+    mpw_pushBuf( buffer, bufferSize, &pushInt, sizeof( pushInt ) );
+}
+
+static void mpw_free(void *const buffer, const size_t bufferSize) {
+
+    memset( buffer, 0, bufferSize );
+    free( buffer );
+}
+
+const uint8_t *mpw_masterKeyForUser(const char *fullName, const char *masterPassword) {
 
-    // Calculate the master key salt.
     const char *mpKeyScope = ScopeForVariant( MPSiteVariantPassword );
-    const uint32_t n_fullNameLength = htonl( strlen( fullName ) );
-    const size_t masterKeySaltLength = strlen( mpKeyScope ) + sizeof( n_fullNameLength ) + strlen( fullName );
-    char *masterKeySalt = (char *)malloc( masterKeySaltLength );
-    if (!masterKeySalt)
-        ftl( "Could not allocate master key salt: %d\n", errno );
-
-    char *mKS = masterKeySalt;
-    memcpy( mKS, mpKeyScope, strlen( mpKeyScope ) );
-    mKS += strlen( mpKeyScope );
-    memcpy( mKS, &n_fullNameLength, sizeof( n_fullNameLength ) );
-    mKS += sizeof( n_fullNameLength );
-    memcpy( mKS, fullName, strlen( fullName ) );
-    mKS += strlen( fullName );
-
     trc( "fullName: %s\n", fullName );
     trc( "masterPassword: %s\n", masterPassword );
     trc( "key scope: %s\n", mpKeyScope );
-    trc( "masterKeySalt ID: %s\n", IDForBuf( masterKeySalt, masterKeySaltLength ) );
-    if (mKS - masterKeySalt != masterKeySaltLength)
-        ftl( "Unexpected master key salt length." );
+
+    // Calculate the master key salt.
+    // masterKeySalt = mpKeyScope . #fullName . fullName
+    size_t masterKeySaltSize = 0;
+    uint8_t *masterKeySalt = NULL;
+    mpw_pushString( &masterKeySalt, &masterKeySaltSize, mpKeyScope );
+    mpw_pushInt( &masterKeySalt, &masterKeySaltSize, htonl( strlen( fullName ) ) );
+    mpw_pushString( &masterKeySalt, &masterKeySaltSize, fullName );
+    if (!masterKeySalt)
+        ftl( "Could not allocate master key salt: %d\n", errno );
+    trc( "masterKeySalt ID: %s\n", IDForBuf( masterKeySalt, masterKeySaltSize ) );
 
     // Calculate the master key.
+    // masterKey = scrypt( masterPassword, masterKeySalt )
     uint8_t *masterKey = (uint8_t *)malloc( MP_dkLen );
-    if (!masterKey) {
-        fprintf( stderr, "Could not allocate master key: %d\n", errno );
-        abort();
-    }
-    if (crypto_scrypt( (const uint8_t *)masterPassword, strlen( masterPassword ), (const uint8_t *)masterKeySalt, masterKeySaltLength, MP_N,
-            MP_r, MP_p, masterKey, MP_dkLen ) < 0) {
-        fprintf( stderr, "Could not generate master key: %d\n", errno );
-        abort();
-    }
-    memset( masterKeySalt, 0, masterKeySaltLength );
-    free( masterKeySalt );
+    if (!masterKey)
+        ftl( "Could not allocate master key: %d\n", errno );
+    if (crypto_scrypt( (const uint8_t *)masterPassword, strlen( masterPassword ),
+            masterKeySalt, masterKeySaltSize, MP_N, MP_r, MP_p, masterKey, MP_dkLen ) < 0)
+        ftl( "Could not generate master key: %d\n", errno );
+    mpw_free( masterKeySalt, masterKeySaltSize );
     trc( "masterKey ID: %s\n", IDForBuf( masterKey, MP_dkLen ) );
 
     return masterKey;
 }
 
-char *mpw_passwordForSite(const uint8_t *masterKey, const char *siteName, const MPSiteType siteType, const uint32_t siteCounter,
+const char *mpw_passwordForSite(const uint8_t *masterKey, const char *siteName, const MPSiteType siteType, const uint32_t siteCounter,
         const MPSiteVariant siteVariant, const char *siteContext) {
 
-    // Calculate the site seed.
+    const char *siteScope = ScopeForVariant( siteVariant );
     trc( "siteName: %s\n", siteName );
     trc( "siteCounter: %d\n", siteCounter );
     trc( "siteVariant: %d\n", siteVariant );
     trc( "siteType: %d\n", siteType );
-    const char *siteScope = ScopeForVariant( siteVariant );
     trc( "site scope: %s, context: %s\n", siteScope, siteContext == NULL? "<empty>": siteContext );
-    const uint32_t n_siteNameLength = htonl( strlen( siteName ) );
-    const uint32_t n_siteCounter = htonl( siteCounter );
-    const uint32_t n_siteContextLength = siteContext == NULL? 0: htonl( strlen( siteContext ) );
-    size_t sitePasswordInfoLength = strlen( siteScope ) + sizeof( n_siteNameLength ) + strlen( siteName ) + sizeof( n_siteCounter );
-    if (siteContext)
-        sitePasswordInfoLength += sizeof( n_siteContextLength ) + strlen( siteContext );
-    char *sitePasswordInfo = (char *)malloc( sitePasswordInfoLength );
-    if (!sitePasswordInfo) {
-        fprintf( stderr, "Could not allocate site seed: %d\n", errno );
-        abort();
-    }
 
-    char *sPI = sitePasswordInfo;
-    memcpy( sPI, siteScope, strlen( siteScope ) );
-    sPI += strlen( siteScope );
-    memcpy( sPI, &n_siteNameLength, sizeof( n_siteNameLength ) );
-    sPI += sizeof( n_siteNameLength );
-    memcpy( sPI, siteName, strlen( siteName ) );
-    sPI += strlen( siteName );
-    memcpy( sPI, &n_siteCounter, sizeof( n_siteCounter ) );
-    sPI += sizeof( n_siteCounter );
+    // Calculate the site seed.
+    // sitePasswordSeed = hmac-sha256( masterKey, siteScope . #siteName . siteName . siteCounter . #siteContext . siteContext )
+    size_t sitePasswordInfoSize = 0;
+    uint8_t *sitePasswordInfo = NULL;
+    mpw_pushString( &sitePasswordInfo, &sitePasswordInfoSize, siteScope );
+    mpw_pushInt( &sitePasswordInfo, &sitePasswordInfoSize, htonl( strlen( siteName ) ) );
+    mpw_pushString( &sitePasswordInfo, &sitePasswordInfoSize, siteName );
+    mpw_pushInt( &sitePasswordInfo, &sitePasswordInfoSize, htonl( siteCounter ) );
     if (siteContext) {
-        memcpy( sPI, &n_siteContextLength, sizeof( n_siteContextLength ) );
-        sPI += sizeof( n_siteContextLength );
-        memcpy( sPI, siteContext, strlen( siteContext ) );
-        sPI += strlen( siteContext );
+        mpw_pushInt( &sitePasswordInfo, &sitePasswordInfoSize, htonl( strlen( siteContext ) ) );
+        mpw_pushString( &sitePasswordInfo, &sitePasswordInfoSize, siteContext );
     }
-    if (sPI - sitePasswordInfo != sitePasswordInfoLength)
-        abort();
-    trc( "seed from: hmac-sha256(masterKey, %s | %s | %s | %s | %s | %s)\n", siteScope,
-            Hex( &n_siteNameLength, sizeof( n_siteNameLength ) ), siteName, Hex( &n_siteCounter, sizeof( n_siteCounter ) ),
-            Hex( &n_siteContextLength, sizeof( n_siteContextLength ) ), siteContext );
-    trc( "sitePasswordInfo ID: %s\n", IDForBuf( sitePasswordInfo, sitePasswordInfoLength ) );
+    if (!sitePasswordInfo)
+        ftl( "Could not allocate site seed: %d\n", errno );
+    trc( "sitePasswordInfo ID: %s\n", IDForBuf( sitePasswordInfo, sitePasswordInfoSize ) );
 
     uint8_t sitePasswordSeed[32];
-    HMAC_SHA256_Buf( masterKey, MP_dkLen, sitePasswordInfo, sitePasswordInfoLength, sitePasswordSeed );
-    memset( sitePasswordInfo, 0, sitePasswordInfoLength );
-    free( sitePasswordInfo );
+    HMAC_SHA256_Buf( masterKey, MP_dkLen, sitePasswordInfo, sitePasswordInfoSize, sitePasswordSeed );
+    mpw_free( sitePasswordInfo, sitePasswordInfoSize );
     trc( "sitePasswordSeed ID: %s\n", IDForBuf( sitePasswordSeed, 32 ) );
 
     // Determine the template.
     const char *template = TemplateForType( siteType, sitePasswordSeed[0] );
     trc( "type %d, template: %s\n", siteType, template );
     if (strlen( template ) > 32)
-        abort();
+        ftl( "Template too long for password seed: %d", strlen( template ) );
 
     // Encode the password from the seed using the template.
-    char *sitePassword = (char *)calloc( strlen( template ) + 1, sizeof( char ) );
+    char *const sitePassword = calloc( strlen( template ) + 1, sizeof( char ) );
     for (int c = 0; c < strlen( template ); ++c) {
         sitePassword[c] = CharacterFromClass( template[c], sitePasswordSeed[c + 1] );
         trc( "class %c, index %u (0x%02X) -> character: %c\n", template[c], sitePasswordSeed[c + 1], sitePasswordSeed[c + 1],
diff --git a/MasterPassword/C/mpw.h b/MasterPassword/C/mpw.h
index a9238599..2d333fd2 100644
--- a/MasterPassword/C/mpw.h
+++ b/MasterPassword/C/mpw.h
@@ -1,6 +1,6 @@
-uint8_t *mpw_masterKeyForUser(
+const uint8_t *mpw_masterKeyForUser(
         const char *fullName, const char *masterPassword);
 
-char *mpw_passwordForSite(
+const char *mpw_passwordForSite(
         const uint8_t *masterKey, const char *siteName, const MPSiteType siteType, const uint32_t siteCounter,
         const MPSiteVariant siteVariant, const char *siteContext);