diff --git a/arch/arm/crypto/poly1305-glue.c b/arch/arm/crypto/poly1305-glue.c
index 3023c1acfa19..c31bd8f7c092 100644
--- a/arch/arm/crypto/poly1305-glue.c
+++ b/arch/arm/crypto/poly1305-glue.c
@@ -29,7 +29,7 @@ void __weak poly1305_blocks_neon(void *state, const u8 *src, u32 len, u32 hibit)
 
 static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
 
-void poly1305_init_arch(struct poly1305_desc_ctx *dctx, const u8 *key)
+void poly1305_init_arch(struct poly1305_desc_ctx *dctx, const u8 key[POLY1305_KEY_SIZE])
 {
 	poly1305_init_arm(&dctx->h, key);
 	dctx->s[0] = get_unaligned_le32(key + 16);
diff --git a/arch/arm64/crypto/poly1305-glue.c b/arch/arm64/crypto/poly1305-glue.c
index f33ada70c4ed..01e22fe40823 100644
--- a/arch/arm64/crypto/poly1305-glue.c
+++ b/arch/arm64/crypto/poly1305-glue.c
@@ -25,7 +25,7 @@ asmlinkage void poly1305_emit(void *state, u8 *digest, const u32 *nonce);
 
 static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_neon);
 
-void poly1305_init_arch(struct poly1305_desc_ctx *dctx, const u8 *key)
+void poly1305_init_arch(struct poly1305_desc_ctx *dctx, const u8 key[POLY1305_KEY_SIZE])
 {
 	poly1305_init_arm64(&dctx->h, key);
 	dctx->s[0] = get_unaligned_le32(key + 16);
diff --git a/arch/mips/crypto/poly1305-glue.c b/arch/mips/crypto/poly1305-glue.c
index fc881b46d911..bc6110fb98e0 100644
--- a/arch/mips/crypto/poly1305-glue.c
+++ b/arch/mips/crypto/poly1305-glue.c
@@ -17,7 +17,7 @@ asmlinkage void poly1305_init_mips(void *state, const u8 *key);
 asmlinkage void poly1305_blocks_mips(void *state, const u8 *src, u32 len, u32 hibit);
 asmlinkage void poly1305_emit_mips(void *state, u8 *digest, const u32 *nonce);
 
-void poly1305_init_arch(struct poly1305_desc_ctx *dctx, const u8 *key)
+void poly1305_init_arch(struct poly1305_desc_ctx *dctx, const u8 key[POLY1305_KEY_SIZE])
 {
 	poly1305_init_mips(&dctx->h, key);
 	dctx->s[0] = get_unaligned_le32(key + 16);
diff --git a/arch/x86/crypto/poly1305_glue.c b/arch/x86/crypto/poly1305_glue.c
index c44aba290fbb..2bc312ffee52 100644
--- a/arch/x86/crypto/poly1305_glue.c
+++ b/arch/x86/crypto/poly1305_glue.c
@@ -16,7 +16,7 @@
 #include <asm/simd.h>
 
 asmlinkage void poly1305_init_x86_64(void *ctx,
-				     const u8 key[POLY1305_KEY_SIZE]);
+				     const u8 key[POLY1305_BLOCK_SIZE]);
 asmlinkage void poly1305_blocks_x86_64(void *ctx, const u8 *inp,
 				       const size_t len, const u32 padbit);
 asmlinkage void poly1305_emit_x86_64(void *ctx, u8 mac[POLY1305_DIGEST_SIZE],
@@ -81,7 +81,7 @@ static void convert_to_base2_64(void *ctx)
 	state->is_base2_26 = 0;
 }
 
-static void poly1305_simd_init(void *ctx, const u8 key[POLY1305_KEY_SIZE])
+static void poly1305_simd_init(void *ctx, const u8 key[POLY1305_BLOCK_SIZE])
 {
 	poly1305_init_x86_64(ctx, key);
 }
@@ -129,7 +129,7 @@ static void poly1305_simd_emit(void *ctx, u8 mac[POLY1305_DIGEST_SIZE],
 		poly1305_emit_avx(ctx, mac, nonce);
 }
 
-void poly1305_init_arch(struct poly1305_desc_ctx *dctx, const u8 *key)
+void poly1305_init_arch(struct poly1305_desc_ctx *dctx, const u8 key[POLY1305_KEY_SIZE])
 {
 	poly1305_simd_init(&dctx->h, key);
 	dctx->s[0] = get_unaligned_le32(&key[16]);
diff --git a/include/crypto/internal/poly1305.h b/include/crypto/internal/poly1305.h
index 064e52ca5248..196aa769f296 100644
--- a/include/crypto/internal/poly1305.h
+++ b/include/crypto/internal/poly1305.h
@@ -18,7 +18,8 @@
  * only the ε-almost-∆-universal hash function (not the full MAC) is computed.
  */
 
-void poly1305_core_setkey(struct poly1305_core_key *key, const u8 *raw_key);
+void poly1305_core_setkey(struct poly1305_core_key *key,
+			  const u8 raw_key[POLY1305_BLOCK_SIZE]);
 static inline void poly1305_core_init(struct poly1305_state *state)
 {
 	*state = (struct poly1305_state){};
diff --git a/include/crypto/poly1305.h b/include/crypto/poly1305.h
index f1f67fc749cf..090692ec3bc7 100644
--- a/include/crypto/poly1305.h
+++ b/include/crypto/poly1305.h
@@ -58,8 +58,10 @@ struct poly1305_desc_ctx {
 	};
 };
 
-void poly1305_init_arch(struct poly1305_desc_ctx *desc, const u8 *key);
-void poly1305_init_generic(struct poly1305_desc_ctx *desc, const u8 *key);
+void poly1305_init_arch(struct poly1305_desc_ctx *desc,
+			const u8 key[POLY1305_KEY_SIZE]);
+void poly1305_init_generic(struct poly1305_desc_ctx *desc,
+			   const u8 key[POLY1305_KEY_SIZE]);
 
 static inline void poly1305_init(struct poly1305_desc_ctx *desc, const u8 *key)
 {
diff --git a/lib/crypto/poly1305-donna32.c b/lib/crypto/poly1305-donna32.c
index 3cc77d94390b..7fb71845cc84 100644
--- a/lib/crypto/poly1305-donna32.c
+++ b/lib/crypto/poly1305-donna32.c
@@ -10,7 +10,8 @@
 #include <asm/unaligned.h>
 #include <crypto/internal/poly1305.h>
 
-void poly1305_core_setkey(struct poly1305_core_key *key, const u8 raw_key[16])
+void poly1305_core_setkey(struct poly1305_core_key *key,
+			  const u8 raw_key[POLY1305_BLOCK_SIZE])
 {
 	/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
 	key->key.r[0] = (get_unaligned_le32(&raw_key[0])) & 0x3ffffff;
diff --git a/lib/crypto/poly1305-donna64.c b/lib/crypto/poly1305-donna64.c
index 6ae181bb4345..d34cf4053668 100644
--- a/lib/crypto/poly1305-donna64.c
+++ b/lib/crypto/poly1305-donna64.c
@@ -12,7 +12,8 @@
 
 typedef __uint128_t u128;
 
-void poly1305_core_setkey(struct poly1305_core_key *key, const u8 raw_key[16])
+void poly1305_core_setkey(struct poly1305_core_key *key,
+			  const u8 raw_key[POLY1305_BLOCK_SIZE])
 {
 	u64 t0, t1;
 
diff --git a/lib/crypto/poly1305.c b/lib/crypto/poly1305.c
index 9d2d14df0fee..26d87fc3823e 100644
--- a/lib/crypto/poly1305.c
+++ b/lib/crypto/poly1305.c
@@ -12,7 +12,8 @@
 #include <linux/module.h>
 #include <asm/unaligned.h>
 
-void poly1305_init_generic(struct poly1305_desc_ctx *desc, const u8 *key)
+void poly1305_init_generic(struct poly1305_desc_ctx *desc,
+			   const u8 key[POLY1305_KEY_SIZE])
 {
 	poly1305_core_setkey(&desc->core_r, key);
 	desc->s[0] = get_unaligned_le32(key + 16);
