crypto: add missing doc comments for public methods (#23864)

vlib/crypto/cipher/cfb.v

@@ -63,6 +63,7 @@ fn new_cfb(b Block, iv []u8, decrypt bool) Cfb {
 	return x
 }
 
+// xor_key_stream xors each byte in the given slice with a byte from the key stream.
 pub fn (mut x Cfb) xor_key_stream(mut dst []u8, src []u8) {
 	unsafe {
 		mut local_dst := *dst

vlib/crypto/cipher/ctr.v

@@ -49,6 +49,7 @@ pub fn new_ctr(b Block, iv []u8) Ctr {
 	}
 }
 
+// xor_key_stream xors each byte in the given slice with a byte from the key stream.
 pub fn (mut x Ctr) xor_key_stream(mut dst []u8, src []u8) {
 	unsafe {
 		mut local_dst := *dst

vlib/crypto/cipher/ofb.v

@@ -35,6 +35,7 @@ pub fn new_ofb(b Block, iv []u8) Ofb {
 	return x
 }
 
+// xor_key_stream xors each byte in the given slice with a byte from the key stream.
 pub fn (mut x Ofb) xor_key_stream(mut dst []u8, src []u8) {
 	unsafe {
 		mut local_dst := *dst

vlib/crypto/des/des.v

@@ -56,6 +56,7 @@ fn (mut c DesCipher) generate_subkeys(key_bytes []u8) {
 	}
 }
 
+// encrypt a block of data using the DES algorithm
 pub fn (c &DesCipher) encrypt(mut dst []u8, src []u8) {
 	if src.len < block_size {
 		panic('crypto/des: input not full block')
@@ -69,6 +70,7 @@ pub fn (c &DesCipher) encrypt(mut dst []u8, src []u8) {
 	encrypt_block(c.subkeys[..], mut dst, src)
 }
 
+// decrypt a block of data using the DES algorithm
 pub fn (c &DesCipher) decrypt(mut dst []u8, src []u8) {
 	if src.len < block_size {
 		panic('crypto/des: input not full block')
@@ -94,6 +96,7 @@ pub fn new_triple_des_cipher(key []u8) cipher.Block {
 	return c
 }
 
+// encrypt a block of data using the TripleDES algorithm
 pub fn (c &TripleDesCipher) encrypt(mut dst []u8, src []u8) {
 	if src.len < block_size {
 		panic('crypto/des: input not full block')
@@ -130,6 +133,7 @@ pub fn (c &TripleDesCipher) encrypt(mut dst []u8, src []u8) {
 	binary.big_endian_put_u64(mut dst, permute_final_block(pre_output))
 }
 
+// decrypt a block of data using the TripleDES algorithm
 pub fn (c &TripleDesCipher) decrypt(mut dst []u8, src []u8) {
 	if src.len < block_size {
 		panic('crypto/des: input not full block')

vlib/crypto/rand/rand.v

@@ -8,6 +8,7 @@ struct ReadError {
 	Error
 }
 
+// msg returns the error message.
 pub fn (err ReadError) msg() string {
 	return 'crypto.rand.read() error reading random bytes'
 }