diff --git a/src/dc_imex.rs b/src/dc_imex.rs
index 1882b4302..bafe83126 100644
--- a/src/dc_imex.rs
+++ b/src/dc_imex.rs
@@ -211,12 +211,8 @@ pub fn dc_render_setup_file(context: &Context, passphrase: &str) -> Result<Strin
     let encr = {
         let private_key_asc_c = CString::yolo(private_key_asc);
         let passphrase_c = CString::yolo(passphrase);
-        dc_pgp_symm_encrypt(
-            passphrase_c.as_ptr(),
-            private_key_asc_c.as_ptr() as *const libc::c_void,
-            private_key_asc_c.as_bytes().len(),
-        )
-        .ok_or(format_err!("Failed to encrypt private key."))?
+        dc_pgp_symm_encrypt(passphrase_c.as_ptr(), private_key_asc_c.as_bytes())
+            .ok_or(format_err!("Failed to encrypt private key."))?
     };
     let replacement = format!(
         concat!(
@@ -449,9 +445,10 @@ pub unsafe fn dc_decrypt_setup_file(
             || binary_bytes == 0)
         {
             /* decrypt symmetrically */
-            if let Some(plain) =
-                dc_pgp_symm_decrypt(passphrase, binary as *const libc::c_void, binary_bytes)
-            {
+            if let Some(plain) = dc_pgp_symm_decrypt(
+                passphrase,
+                std::slice::from_raw_parts(binary as *const u8, binary_bytes),
+            ) {
                 let payload_c = CString::new(plain).unwrap();
                 payload = strdup(payload_c.as_ptr());
             }
diff --git a/src/e2ee.rs b/src/e2ee.rs
index b172b694f..9a84ce17a 100644
--- a/src/e2ee.rs
+++ b/src/e2ee.rs
@@ -299,8 +299,10 @@ impl E2eeHelper {
                                 ok_to_continue = false;
                             } else {
                                 if let Some(ctext_v) = dc_pgp_pk_encrypt(
-                                    (*plain).str_0 as *const libc::c_void,
-                                    (*plain).len,
+                                    std::slice::from_raw_parts(
+                                        (*plain).str_0 as *const u8,
+                                        (*plain).len,
+                                    ),
                                     &keyring,
                                     sign_key.as_ref(),
                                 ) {
@@ -907,8 +909,7 @@ unsafe fn decrypt_part(
 
                 /*if we already have fingerprints, do not add more; this ensures, only the fingerprints from the outer-most part are collected */
                 if let Some(plain) = dc_pgp_pk_decrypt(
-                    decoded_data as *const libc::c_void,
-                    decoded_data_bytes,
+                    std::slice::from_raw_parts(decoded_data as *const u8, decoded_data_bytes),
                     &private_keyring,
                     &public_keyring_for_validate,
                     add_signatures,
diff --git a/src/pgp.rs b/src/pgp.rs
index 4ed43edea..46d1fc8b0 100644
--- a/src/pgp.rs
+++ b/src/pgp.rs
@@ -188,15 +188,11 @@ pub fn dc_pgp_create_keypair(addr: impl AsRef<str>) -> Option<(Key, Key)> {
 }
 
 pub fn dc_pgp_pk_encrypt(
-    plain_text: *const libc::c_void,
-    plain_bytes: size_t,
+    plain: &[u8],
     public_keys_for_encryption: &Keyring,
     private_key_for_signing: Option<&Key>,
 ) -> Option<String> {
-    assert!(!plain_text.is_null() && !plain_bytes > 0, "invalid input");
-
-    let bytes = unsafe { std::slice::from_raw_parts(plain_text as *const u8, plain_bytes) };
-    let lit_msg = Message::new_literal_bytes("", bytes);
+    let lit_msg = Message::new_literal_bytes("", plain);
     let pkeys: Vec<&SignedPublicKey> = public_keys_for_encryption
         .keys()
         .into_iter()
@@ -227,16 +223,11 @@ pub fn dc_pgp_pk_encrypt(
 }
 
 pub fn dc_pgp_pk_decrypt(
-    ctext: *const libc::c_void,
-    ctext_bytes: size_t,
+    ctext: &[u8],
     private_keys_for_decryption: &Keyring,
     public_keys_for_validation: &Keyring,
     ret_signature_fingerprints: Option<&mut HashSet<String>>,
 ) -> Option<Vec<u8>> {
-    assert!(!ctext.is_null() && ctext_bytes > 0, "invalid input");
-
-    let ctext = unsafe { std::slice::from_raw_parts(ctext as *const u8, ctext_bytes) };
-
     // TODO: proper error handling
     if let Ok((msg, _)) = Message::from_armor_single(Cursor::new(ctext)) {
         let skeys: Vec<&SignedSecretKey> = private_keys_for_decryption
@@ -283,19 +274,13 @@ pub fn dc_pgp_pk_decrypt(
 }
 
 /// Symmetric encryption.
-pub fn dc_pgp_symm_encrypt(
-    passphrase: *const libc::c_char,
-    plain: *const libc::c_void,
-    plain_bytes: size_t,
-) -> Option<String> {
+pub fn dc_pgp_symm_encrypt(passphrase: *const libc::c_char, plain: &[u8]) -> Option<String> {
     assert!(!passphrase.is_null(), "invalid passphrase");
-    assert!(!plain.is_null() && !plain_bytes > 0, "invalid input");
 
     let pw = unsafe { CStr::from_ptr(passphrase).to_str().unwrap() };
-    let bytes = unsafe { std::slice::from_raw_parts(plain as *const u8, plain_bytes) };
 
     let mut rng = thread_rng();
-    let lit_msg = Message::new_literal_bytes("", bytes);
+    let lit_msg = Message::new_literal_bytes("", plain);
 
     let s2k = StringToKey::new_default(&mut rng);
     let msg = lit_msg.encrypt_with_password(&mut rng, s2k, Default::default(), || pw.into());
@@ -304,18 +289,12 @@ pub fn dc_pgp_symm_encrypt(
 }
 
 /// Symmetric decryption.
-pub fn dc_pgp_symm_decrypt(
-    passphrase: *const libc::c_char,
-    ctext: *const libc::c_void,
-    ctext_bytes: size_t,
-) -> Option<Vec<u8>> {
+pub fn dc_pgp_symm_decrypt(passphrase: *const libc::c_char, ctext: &[u8]) -> Option<Vec<u8>> {
     assert!(!passphrase.is_null(), "invalid passphrase");
-    assert!(!ctext.is_null() && !ctext_bytes > 0, "invalid input");
 
     let pw = unsafe { CStr::from_ptr(passphrase).to_str().unwrap() };
-    let bytes = unsafe { std::slice::from_raw_parts(ctext as *const u8, ctext_bytes) };
 
-    let enc_msg = Message::from_bytes(Cursor::new(bytes));
+    let enc_msg = Message::from_bytes(Cursor::new(ctext));
 
     enc_msg
         .and_then(|msg| {
diff --git a/tests/stress.rs b/tests/stress.rs
index 3795f98d7..ab903f727 100644
--- a/tests/stress.rs
+++ b/tests/stress.rs
@@ -1,7 +1,6 @@
 //! Stress some functions for testing; if used as a lib, this file is obsolete.
 
 use std::collections::HashSet;
-use std::ffi::CString;
 use std::ptr;
 
 use tempfile::{tempdir, TempDir};
@@ -494,39 +493,20 @@ fn test_encryption_decryption() {
 
         assert_ne!(public_key, public_key2);
 
-        let original_text: *const libc::c_char =
-            b"This is a test\x00" as *const u8 as *const libc::c_char;
+        let original_text = b"This is a test";
         let mut keyring = Keyring::default();
         keyring.add_owned(public_key.clone());
         keyring.add_ref(&public_key2);
 
-        let ctext = dc_pgp_pk_encrypt(
-            original_text as *const libc::c_void,
-            strlen(original_text),
-            &keyring,
-            Some(&private_key),
-        )
-        .unwrap();
+        let ctext = dc_pgp_pk_encrypt(original_text, &keyring, Some(&private_key)).unwrap();
 
         assert!(!ctext.is_empty());
         assert!(ctext.starts_with("-----BEGIN PGP MESSAGE-----"));
 
-        let ctext_signed_bytes = ctext.len();
-        let ctext_signed = CString::yolo(ctext);
-
-        let ctext = dc_pgp_pk_encrypt(
-            original_text as *const libc::c_void,
-            strlen(original_text),
-            &keyring,
-            None,
-        )
-        .unwrap();
+        let ctext = dc_pgp_pk_encrypt(original_text, &keyring, None).unwrap();
         assert!(!ctext.is_empty());
         assert!(ctext.starts_with("-----BEGIN PGP MESSAGE-----"));
 
-        let ctext_unsigned_bytes = ctext.len();
-        let ctext_unsigned = CString::yolo(ctext);
-
         let mut keyring = Keyring::default();
         keyring.add_owned(private_key);
 
@@ -539,42 +519,39 @@ fn test_encryption_decryption() {
         let mut valid_signatures: HashSet<String> = Default::default();
 
         let plain = dc_pgp_pk_decrypt(
-            ctext_signed.as_ptr() as *const _,
-            ctext_signed_bytes,
+            ctext.as_bytes(),
             &keyring,
             &public_keyring,
             Some(&mut valid_signatures),
         )
         .unwrap();
 
-        assert_eq!(std::str::from_utf8(&plain).unwrap(), as_str(original_text),);
+        assert_eq!(plain, original_text,);
         assert_eq!(valid_signatures.len(), 1);
 
         valid_signatures.clear();
 
         let empty_keyring = Keyring::default();
         let plain = dc_pgp_pk_decrypt(
-            ctext_signed.as_ptr() as *const _,
-            ctext_signed_bytes,
+            ctext.as_bytes(),
             &keyring,
             &empty_keyring,
             Some(&mut valid_signatures),
         )
         .unwrap();
-        assert_eq!(std::str::from_utf8(&plain).unwrap(), as_str(original_text),);
+        assert_eq!(plain, original_text);
         assert_eq!(valid_signatures.len(), 0);
 
         valid_signatures.clear();
 
         let plain = dc_pgp_pk_decrypt(
-            ctext_signed.as_ptr() as *const _,
-            ctext_signed_bytes,
+            ctext.as_bytes(),
             &keyring,
             &public_keyring2,
             Some(&mut valid_signatures),
         )
         .unwrap();
-        assert_eq!(std::str::from_utf8(&plain).unwrap(), as_str(original_text),);
+        assert_eq!(plain, original_text);
         assert_eq!(valid_signatures.len(), 0);
 
         valid_signatures.clear();
@@ -582,28 +559,26 @@ fn test_encryption_decryption() {
         public_keyring2.add_ref(&public_key);
 
         let plain = dc_pgp_pk_decrypt(
-            ctext_signed.as_ptr() as *const _,
-            ctext_signed_bytes,
+            ctext.as_bytes(),
             &keyring,
             &public_keyring2,
             Some(&mut valid_signatures),
         )
         .unwrap();
-        assert_eq!(std::str::from_utf8(&plain).unwrap(), as_str(original_text),);
+        assert_eq!(plain, original_text);
         assert_eq!(valid_signatures.len(), 1);
 
         valid_signatures.clear();
 
         let plain = dc_pgp_pk_decrypt(
-            ctext_unsigned.as_ptr() as *const _,
-            ctext_unsigned_bytes,
+            ctext.as_bytes(),
             &keyring,
             &public_keyring,
             Some(&mut valid_signatures),
         )
         .unwrap();
 
-        assert_eq!(std::str::from_utf8(&plain).unwrap(), as_str(original_text),);
+        assert_eq!(plain, original_text);
 
         valid_signatures.clear();
 
@@ -612,16 +587,9 @@ fn test_encryption_decryption() {
         let mut public_keyring = Keyring::default();
         public_keyring.add_ref(&public_key);
 
-        let plain = dc_pgp_pk_decrypt(
-            ctext_signed.as_ptr() as *const _,
-            ctext_signed_bytes,
-            &keyring,
-            &public_keyring,
-            None,
-        )
-        .unwrap();
+        let plain = dc_pgp_pk_decrypt(ctext.as_bytes(), &keyring, &public_keyring, None).unwrap();
 
-        assert_eq!(std::str::from_utf8(&plain).unwrap(), as_str(original_text),);
+        assert_eq!(plain, original_text);
     }
 }