diff --git a/vlib/crypto/aes/aes.v b/vlib/crypto/aes/aes.v
index a159048f3e..bf9edafb15 100644
--- a/vlib/crypto/aes/aes.v
+++ b/vlib/crypto/aes/aes.v
@@ -24,6 +24,18 @@ mut:
 	dec []u32
 }
 
+// free the resources taken by the AesCipher `c`
+[unsafe]
+pub fn (mut c AesCipher) free() {
+	$if prealloc {
+		return
+	}
+	unsafe {
+		c.enc.free()
+		c.dec.free()
+	}
+}
+
 // new_cipher creates and returns a new [[AesCipher](#AesCipher)].
 // The key argument should be the AES key,
 // either 16, 24, or 32 bytes to select
diff --git a/vlib/crypto/bcrypt/bcrypt.v b/vlib/crypto/bcrypt/bcrypt.v
index 9398959d42..b396552dcf 100644
--- a/vlib/crypto/bcrypt/bcrypt.v
+++ b/vlib/crypto/bcrypt/bcrypt.v
@@ -27,6 +27,18 @@ mut:
 	minor string
 }
 
+// free the resources taken by the Hashed `h`
+[unsafe]
+pub fn (mut h Hashed) free() {
+	$if prealloc {
+		return
+	}
+	unsafe {
+		h.salt.free()
+		h.hash.free()
+	}
+}
+
 const magic_cipher_data = [u8(0x4f), 0x72, 0x70, 0x68, 0x65, 0x61, 0x6e, 0x42, 0x65, 0x68, 0x6f,
 	0x6c, 0x64, 0x65, 0x72, 0x53, 0x63, 0x72, 0x79, 0x44, 0x6f, 0x75, 0x62, 0x74]
 
diff --git a/vlib/crypto/cipher/cbc.v b/vlib/crypto/cipher/cbc.v
index 67730e3d8e..2e901700a0 100644
--- a/vlib/crypto/cipher/cbc.v
+++ b/vlib/crypto/cipher/cbc.v
@@ -19,6 +19,19 @@ mut:
 	tmp        []u8
 }
 
+// free the resources taken by the Cbc `x`
+[unsafe]
+pub fn (mut x Cbc) free() {
+	$if prealloc {
+		return
+	}
+	unsafe {
+		// x.b.free() TODO add?
+		x.iv.free()
+		x.tmp.free()
+	}
+}
+
 // internal
 fn new_des_cbc(b Block, iv []u8) Cbc {
 	return Cbc{
diff --git a/vlib/crypto/cipher/cfb.v b/vlib/crypto/cipher/cfb.v
index a2853df914..527a3ab007 100644
--- a/vlib/crypto/cipher/cfb.v
+++ b/vlib/crypto/cipher/cfb.v
@@ -20,6 +20,19 @@ mut:
 	decrypt bool
 }
 
+// free the resources taken by the Cfb `x`
+[unsafe]
+pub fn (mut x Cfb) free() {
+	$if prealloc {
+		return
+	}
+	unsafe {
+		// x.b.free() TODO add?
+		x.out.free()
+		x.next.free()
+	}
+}
+
 // new_cfb_encrypter returns a `Cfb` which encrypts with cipher feedback mode,
 // using the given Block. The iv must be the same length as the Block's block
 // size
diff --git a/vlib/crypto/cipher/ctr.v b/vlib/crypto/cipher/ctr.v
index b23be26257..fc8962ce99 100644
--- a/vlib/crypto/cipher/ctr.v
+++ b/vlib/crypto/cipher/ctr.v
@@ -21,6 +21,19 @@ mut:
 	out_used int
 }
 
+// free the resources taken by the Ctr `c`
+[unsafe]
+pub fn (mut x Ctr) free() {
+	$if prealloc {
+		return
+	}
+	unsafe {
+		// x.b.free() TODO add?
+		x.out.free()
+		x.next.free()
+	}
+}
+
 // new_ctr returns a Ctr which encrypts/decrypts using the given Block in
 // counter mode. The length of iv must be the same as the Block's block size.
 pub fn new_ctr(b Block, iv []u8) Ctr {
diff --git a/vlib/crypto/md5/md5.v b/vlib/crypto/md5/md5.v
index 6a6dc49f90..1450ba0f2d 100644
--- a/vlib/crypto/md5/md5.v
+++ b/vlib/crypto/md5/md5.v
@@ -33,9 +33,23 @@ mut:
 	len u64
 }
 
-fn (mut d Digest) reset() {
+// free the resources taken by the Digest `d`
+[unsafe]
+pub fn (mut d Digest) free() {
+	$if prealloc {
+		return
+	}
+	unsafe { d.x.free() }
+}
+
+fn (mut d Digest) init() {
 	d.s = []u32{len: (4)}
 	d.x = []u8{len: md5.block_size}
+	d.reset()
+}
+
+// reset the state of the Digest `d`
+pub fn (mut d Digest) reset() {
 	d.s[0] = u32(md5.init0)
 	d.s[1] = u32(md5.init1)
 	d.s[2] = u32(md5.init2)
@@ -47,7 +61,7 @@ fn (mut d Digest) reset() {
 // new returns a new Digest (implementing hash.Hash) computing the MD5 checksum.
 pub fn new() &Digest {
 	mut d := &Digest{}
-	d.reset()
+	d.init()
 	return d
 }
 
diff --git a/vlib/crypto/md5/md5_test.v b/vlib/crypto/md5/md5_test.v
index 0081a8fd77..6edf166beb 100644
--- a/vlib/crypto/md5/md5_test.v
+++ b/vlib/crypto/md5/md5_test.v
@@ -6,3 +6,23 @@ import crypto.md5
 fn test_crypto_md5() {
 	assert md5.sum('this is a md5 checksum.'.bytes()).hex() == '6fb421ff99036547655984da12973431'
 }
+
+fn test_crypto_md5_writer() {
+	mut digest := md5.new()
+	digest.write('this is a'.bytes()) or { assert false }
+	digest.write(' md5 checksum.'.bytes()) or { assert false }
+	sum := digest.sum([])
+	assert sum.hex() == '6fb421ff99036547655984da12973431'
+}
+
+fn test_crypto_md5_writer_reset() {
+	mut digest := md5.new()
+	digest.write('this is a'.bytes()) or { assert false }
+	digest.write(' md5 checksum.'.bytes()) or { assert false }
+	_ = digest.sum([])
+	digest.reset()
+	digest.write('this is a'.bytes()) or { assert false }
+	digest.write(' md5 checksum.'.bytes()) or { assert false }
+	sum := digest.sum([])
+	assert sum.hex() == '6fb421ff99036547655984da12973431'
+}
diff --git a/vlib/crypto/rc4/rc4.v b/vlib/crypto/rc4/rc4.v
index cf533a2bde..dc5f5595d1 100644
--- a/vlib/crypto/rc4/rc4.v
+++ b/vlib/crypto/rc4/rc4.v
@@ -20,6 +20,15 @@ mut:
 	j u8
 }
 
+// free the resources taken by the Cipher `c`
+[unsafe]
+pub fn (mut c Cipher) free() {
+	$if prealloc {
+		return
+	}
+	unsafe { c.s.free() }
+}
+
 // new_cipher creates and returns a new Cipher. The key argument should be the
 // RC4 key, at least 1 byte and at most 256 bytes.
 pub fn new_cipher(key []u8) !Cipher {
diff --git a/vlib/crypto/sha1/sha1.v b/vlib/crypto/sha1/sha1.v
index 4f7622c38d..96084e4705 100644
--- a/vlib/crypto/sha1/sha1.v
+++ b/vlib/crypto/sha1/sha1.v
@@ -35,9 +35,26 @@ mut:
 	len u64
 }
 
-fn (mut d Digest) reset() {
+// free the resources taken by the Digest `d`
+[unsafe]
+pub fn (mut d Digest) free() {
+	$if prealloc {
+		return
+	}
+	unsafe {
+		d.x.free()
+		d.h.free()
+	}
+}
+
+fn (mut d Digest) init() {
 	d.x = []u8{len: sha1.chunk}
 	d.h = []u32{len: (5)}
+	d.reset()
+}
+
+// reset the state of the Digest `d`
+pub fn (mut d Digest) reset() {
 	d.h[0] = u32(sha1.init0)
 	d.h[1] = u32(sha1.init1)
 	d.h[2] = u32(sha1.init2)
@@ -50,7 +67,7 @@ fn (mut d Digest) reset() {
 // new returns a new Digest (implementing hash.Hash) computing the SHA1 checksum.
 pub fn new() &Digest {
 	mut d := &Digest{}
-	d.reset()
+	d.init()
 	return d
 }
 
diff --git a/vlib/crypto/sha1/sha1_test.v b/vlib/crypto/sha1/sha1_test.v
index b063d8aec4..e9a4b52421 100644
--- a/vlib/crypto/sha1/sha1_test.v
+++ b/vlib/crypto/sha1/sha1_test.v
@@ -6,3 +6,23 @@ import crypto.sha1
 fn test_crypto_sha1() {
 	assert sha1.sum('This is a sha1 checksum.'.bytes()).hex() == 'e100d74442faa5dcd59463b808983c810a8eb5a1'
 }
+
+fn test_crypto_sha1_writer() {
+	mut digest := sha1.new()
+	digest.write('This is a'.bytes()) or { assert false }
+	digest.write(' sha1 checksum.'.bytes()) or { assert false }
+	sum := digest.sum([])
+	assert sum.hex() == 'e100d74442faa5dcd59463b808983c810a8eb5a1'
+}
+
+fn test_crypto_sha1_writer_reset() {
+	mut digest := sha1.new()
+	digest.write('This is a'.bytes()) or { assert false }
+	digest.write(' sha1 checksum.'.bytes()) or { assert false }
+	_ = digest.sum([])
+	digest.reset()
+	digest.write('This is a'.bytes()) or { assert false }
+	digest.write(' sha1 checksum.'.bytes()) or { assert false }
+	sum := digest.sum([])
+	assert sum.hex() == 'e100d74442faa5dcd59463b808983c810a8eb5a1'
+}
diff --git a/vlib/crypto/sha256/sha256.v b/vlib/crypto/sha256/sha256.v
index 89638bce4c..717fb58275 100644
--- a/vlib/crypto/sha256/sha256.v
+++ b/vlib/crypto/sha256/sha256.v
@@ -63,6 +63,7 @@ pub fn (mut d Digest) free() {
 fn (mut d Digest) init() {
 	d.h = []u32{len: (8)}
 	d.x = []u8{len: sha256.chunk}
+	d.reset()
 }
 
 // reset the state of the Digest `d`
@@ -94,7 +95,6 @@ pub fn (mut d Digest) reset() {
 pub fn new() &Digest {
 	mut d := &Digest{}
 	d.init()
-	d.reset()
 	return d
 }
 
@@ -103,7 +103,6 @@ pub fn new224() &Digest {
 	mut d := &Digest{}
 	d.is224 = true
 	d.init()
-	d.reset()
 	return d
 }
 
diff --git a/vlib/crypto/sha512/sha512.v b/vlib/crypto/sha512/sha512.v
index 56e559dc98..af68ccf2fd 100644
--- a/vlib/crypto/sha512/sha512.v
+++ b/vlib/crypto/sha512/sha512.v
@@ -70,9 +70,26 @@ mut:
 	function crypto.Hash
 }
 
-fn (mut d Digest) reset() {
+// free the resources taken by the Digest `d`
+[unsafe]
+pub fn (mut d Digest) free() {
+	$if prealloc {
+		return
+	}
+	unsafe {
+		d.x.free()
+		d.h.free()
+	}
+}
+
+fn (mut d Digest) init() {
 	d.h = []u64{len: (8)}
 	d.x = []u8{len: sha512.chunk}
+	d.reset()
+}
+
+// reset the state of the Digest `d`
+pub fn (mut d Digest) reset() {
 	match d.function {
 		.sha384 {
 			d.h[0] = sha512.init0_384
@@ -124,7 +141,7 @@ fn new_digest(hash crypto.Hash) &Digest {
 	mut d := &Digest{
 		function: hash
 	}
-	d.reset()
+	d.init()
 	return d
 }
 
diff --git a/vlib/crypto/sha512/sha512_test.v b/vlib/crypto/sha512/sha512_test.v
index cfc96d76fe..624602d893 100644
--- a/vlib/crypto/sha512/sha512_test.v
+++ b/vlib/crypto/sha512/sha512_test.v
@@ -6,3 +6,23 @@ import crypto.sha512
 fn test_crypto_sha512() {
 	assert sha512.sum512('This is a sha512 checksum.'.bytes()).hex() == '4143e55fcba7e39b20f62a1368e5eb28f64a8859458886117ac66027832e0f9f5263daec688c439d2d0fa07059334668d39e59543039703dbb7e03ec9da7f8d7'
 }
+
+fn test_crypto_sha512_writer() {
+	mut digest := sha512.new_digest(.sha512)
+	digest.write('This is a'.bytes()) or { assert false }
+	digest.write(' sha512 checksum.'.bytes()) or { assert false }
+	sum := digest.checksum()
+	assert sum.hex() == '4143e55fcba7e39b20f62a1368e5eb28f64a8859458886117ac66027832e0f9f5263daec688c439d2d0fa07059334668d39e59543039703dbb7e03ec9da7f8d7'
+}
+
+fn test_crypto_sha512_writer_reset() {
+	mut digest := sha512.new_digest(.sha512)
+	digest.write('This is a'.bytes()) or { assert false }
+	digest.write(' sha512 checksum.'.bytes()) or { assert false }
+	_ = digest.checksum()
+	digest.reset()
+	digest.write('This is a'.bytes()) or { assert false }
+	digest.write(' sha512 checksum.'.bytes()) or { assert false }
+	sum := digest.checksum()
+	assert sum.hex() == '4143e55fcba7e39b20f62a1368e5eb28f64a8859458886117ac66027832e0f9f5263daec688c439d2d0fa07059334668d39e59543039703dbb7e03ec9da7f8d7'
+}