diff --git a/src/testdir/test_crypt.vim b/src/testdir/test_crypt.vim
index f386593..63bf8a5 100644
--- a/src/testdir/test_crypt.vim
+++ b/src/testdir/test_crypt.vim
@@ -22,6 +22,11 @@
   call Common_head_only('VimCrypt~03!abc')
 endfunc
 
+func Test_head_only_4()
+  CheckFeature sodium
+  call Common_head_only('VimCrypt~04!abc')
+endfunc
+
 func Crypt_uncrypt(method)
   exe "set cryptmethod=" . a:method
   " If the blowfish test fails 'cryptmethod' will be 'zip' now.
@@ -55,6 +60,11 @@
   call Crypt_uncrypt('blowfish2')
 endfunc
 
+func Test_crypt_sodium()
+  CheckFeature sodium
+  call Crypt_uncrypt('xchacha20')
+endfunc
+
 func Uncrypt_stable(method, crypted_text, key, uncrypted_text)
   split Xtest.txt
   set bin noeol key= fenc=latin1
@@ -70,6 +80,16 @@
   set key=
 endfunc
 
+func Uncrypt_stable_xxd(method, hex, key, uncrypted_text)
+  " use xxd to write the binary content
+  call system('xxd -r >Xtest.txt', a:hex)
+  call feedkeys(":split Xtest.txt\<CR>" . a:key . "\<CR>", 'xt')
+  call assert_equal(a:uncrypted_text, getline(1, len(a:uncrypted_text)))
+  bwipe!
+  call delete('Xtest.txt')
+  set key=
+endfunc
+
 func Test_uncrypt_zip()
   call Uncrypt_stable('zip', "VimCrypt~01!\u0006\u001clV'\u00de}Mg\u00a0\u00ea\u00a3V\u00a9\u00e7\u0007E#3\u008e2U\u00e9\u0097", "foofoo", ["1234567890", "aábbccddeëff"])
 endfunc
@@ -78,10 +98,115 @@
   call Uncrypt_stable('blowfish', "VimCrypt~02!k)\u00be\u0017\u0097#\u0016\u00ddS\u009c\u00f5=\u00ba\u00e0\u00c8#\u00a5M\u00b4\u0086J\u00c3A\u00cd\u00a5M\u00b4\u0086!\u0080\u0015\u009b\u00f5\u000f\u00e1\u00d2\u0019\u0082\u0016\u0098\u00f7\u000d\u00da", "barbar", ["asdfasdfasdf", "0001112223333"])
 endfunc
 
-func Test_uncrypt_blowfish2()
+func Test_uncrypt_blowfish2a()
   call Uncrypt_stable('blowfish', "VimCrypt~03!\u001e\u00d1N\u00e3;\u00d3\u00c0\u00a0^C)\u0004\u00f7\u007f.\u00b6\u00abF\u000eS\u0019\u00e0\u008b6\u00d2[T\u00cb\u00a7\u0085\u00d8\u00be9\u000b\u00812\u000bQ\u00b3\u00cc@\u0097\u000f\u00df\u009a\u00adIv\u00aa.\u00d8\u00c9\u00ee\u009e`\u00bd$\u00af%\u00d0", "barburp", ["abcdefghijklmnopqrstuvwxyz", "!@#$%^&*()_+=-`~"])
 endfunc
 
+func Test_uncrypt_blowfish2()
+  call Uncrypt_stable('blowfish2', "VimCrypt~03!\u001e\u00d1N\u00e3;\u00d3\u00c0\u00a0^C)\u0004\u00f7\u007f.\u00b6\u00abF\u000eS\u0019\u00e0\u008b6\u00d2[T\u00cb\u00a7\u0085\u00d8\u00be9\u000b\u00812\u000bQ\u00b3\u00cc@\u0097\u000f\u00df\u009a\u00adIv\u00aa.\u00d8\u00c9\u00ee\u009e`\u00bd$\u00af%\u00d0", "barburp", ["abcdefghijklmnopqrstuvwxyz", "!@#$%^&*()_+=-`~"])
+endfunc
+
+func Test_uncrypt_xchacha20()
+  CheckFeature sodium
+  let hex=['00000000: 5669 6d43 7279 7074 7e30 3421 6b7d e607  vimCrypt~04!k}..',
+        \  '00000010: 4ea4 e99f 923e f67f 7b59 a80d 3bca 2f06  N....>..{Y..;./.',
+        \  '00000020: fa11 b951 8d09 0dc9 470f e7cf 8b90 4310  ...Q....G.....C.',
+        \  '00000030: 653b b83b e493 378b 0390 0e38 f912 626b  e;.;..7....8..bk',
+        \  '00000040: a02e 4697 0254 2625 2d8e 3a0b 784b e89c  ..F..T&%-.:.xK..',
+        \  '00000050: 0c67 a975 3c17 9319 8ffd 1463 7783 a1f3  .g.u<......cw...',
+        \  '00000060: d917 dcb3 8b3e ecd7 c7d4 086b 6059 7ead  .....>.....k`Y~.',
+        \  '00000070: 9b07 f96b 5c1b 4d08 cd91 f208 5221 7484  ...k\.M.....R!t.',
+        \  '00000080: 72be 0136 84a1 d3                        r..6...']
+  " the file should be in latin1 encoding, this makes sure that readfile()
+  " retries several times converting the multi-byte characters
+  call Uncrypt_stable_xxd('xchacha20', hex, "sodium_crypt", ["abcdefghijklmnopqrstuvwxyzäöü", "ZZZ_äüöÄÜÖ_!@#$%^&*()_+=-`~"])
+endfunc
+
+func Test_uncrypt_xchacha20_invalid()
+  CheckFeature sodium
+  " load an invalid encrypted file and verify it can be decrypted with an
+  " error message
+  try
+    call feedkeys(":split samples/crypt_sodium_invalid.txt\<CR>sodium\<CR>", 'xt')
+    call assert_false(1, 'should not happen')
+  catch
+    call assert_exception('pre-mature')
+  endtry
+  call assert_match("Note: Encryption of swapfile not supported, disabling swap- and undofile", execute(':5messages'))
+
+  call assert_equal(0, &swapfile)
+  call assert_equal("xchacha20", &cryptmethod)
+  call assert_equal('311111111111111111111111', getline('$'))
+  bw!
+endfunc
+
+func Test_uncrypt_xchacha20_2()
+  CheckFeature sodium
+  sp Xcrypt_sodium.txt
+  " Create a larger file, so that Vim will write in several blocks
+  call setline(1, range(1,4000))
+  call assert_equal(1, &swapfile)
+  set cryptmethod=xchacha20
+  call feedkeys(":X\<CR>sodium\<CR>sodium\<CR>", 'xt')
+  " swapfile disabled
+  call assert_equal(0, &swapfile)
+  call assert_match("Note: Encryption of swapfile not supported, disabling swap- and undofile", execute(':messages'))
+  w!
+  " encrypted using xchacha20
+  call assert_match("\[xchacha20\]", execute(':messages'))
+  bw!
+  call feedkeys(":sp Xcrypt_sodium.txt\<CR>sodium\<CR>", 'xt')
+  " successfully decrypted
+  call assert_equal(range(1, 4000)->map( {_, v -> string(v)}), getline(1,'$'))
+  set key=
+  w!
+  " enryption removed
+  call assert_match('"Xcrypt_sodium.txt" 4000L, 18893B written', execute(':message'))
+  bw!
+  call delete('Xcrypt_sodium.txt')
+  set cryptmethod&vim
+endfunc
+
+func Test_uncrypt_xchacha20_3_persistent_undo()
+  CheckFeature sodium
+  CheckFeature persistent_undo
+  sp Xcrypt_sodium_undo.txt
+  set cryptmethod=xchacha20 undofile
+  call feedkeys(":X\<CR>sodium\<CR>sodium\<CR>", 'xt')
+  call assert_equal(0, &undofile)
+  let ufile=undofile(@%)
+  call append(0, ['monday', 'tuesday', 'wednesday', 'thursday', 'friday'])
+  call cursor(1, 1)
+
+  set undolevels=100
+  normal dd
+  set undolevels=100
+  normal dd
+  set undolevels=100
+  normal dd
+  set undolevels=100
+  w!
+  bw!
+  call feedkeys(":sp Xcrypt_sodium_undo.txt\<CR>sodium\<CR>", 'xt')
+  " should fail
+  norm! u
+  call assert_match('Already at oldest change', execute(':1mess'))
+  call assert_fails('verbose rundo' .. fnameescape(ufile), 'E822')
+  bw!
+  set undolevels& cryptmethod& undofile&
+  call delete('Xcrypt_sodium_undo.txt')
+endfunc
+
+func Test_encrypt_xchacha20_missing()
+  if has("sodium")
+    return
+  endif
+  sp Xcrypt_sodium_undo.txt
+  call assert_fails(':set cryptmethod=xchacha20', 'E474')
+  bw!
+  set cm&
+endfunc
+
 func Test_uncrypt_unknown_method()
   split Xuncrypt_unknown.txt
   set bin noeol key= fenc=latin1